Download File - Mr. Heff`s Class

1
UNIT 3
ORGANIC CHEMISTRY
What is organic chemistry?
-The study of molecular compounds containing carbon and hydrogen atoms. Exs: CH4, CH3OH, CH3NH2, etc.
-Properties of organic compounds result from the covalent bonds with their molecules.
Origins of Organic Chemistry
•Swedish chemist Jons Jacob Berzelius classified compounds in 2 categories
1)Organic
•Obtained from living organisms
•Most chemists believed organics could only be synthesized in living organisms thus the theory of “vitalism”
2)Inorganic
•Obtained from mineral sources (non-living)
-German chemist Friedrich Wohler discovered that organic compounds could be synthesized from inorganic
compounds.
–Performed experiment with ammonium cyanate to synthesize urea (found in urine of living creatures).
NH4OCN(aq)  (NH2)2CO(s)
–Acetic acid, CH3COOH; Sucrose, C12H22O11, as well as many others were and are synthesized
Uniqueness of Carbon
1) Form four bonds with other atoms
2) Bond together to form chains, rings, spheres, sheets and tubes of almost any size
3)
Ability to form single, double and triple covalent bonds
Is this why we have so many organic compounds? YES!
These unique properties explain why the number of known compounds of carbon far exceeds the number of
compounds of all other elements combined. Today, over 98% of all known compounds are organic.
Comparing Inorganic & Organic Compounds
Organic Compounds
Inorganic Compounds
covalent bonding (share electrons)
mainly ionic bonding (transfer electrons)
lower melting
higher melting
do not conduct electricity
conduct electricity
Natural sources: Organic Compounds
1) Carbonized organic matter such as Fossil fuels (once living matter) ex: coal, oil, and natural gas
2
2) From plants and animals (living organisms) Ex - penicillin from mold and ASA from the bark of a willow tree
Inorganic can be extracted from mineral sources (non-living).
Synthetic organic compounds such as gasoline, solvents, polyesters, synthetic sweeteners, artificial flavors (vanilla flavor),
and medicines (antibiotics, aspirin, heart drugs) have been invented by chemists and engineers. These are copies of the
natural products produced by plants and animals
Two Classes of Compounds
1) Organic Compounds are compounds that have a combination of carbon and hydrogen
2) Inorganic Compounds are compounds that have either carbon or hydrogen. They contained ionic bonds. They
include all oxides of carbon (CO2, CO), carbonates (CO32-,HCO3-), cyanides (CN-, SCN-), carbides (SiC)
TWO CLASSES OF ORGANIC COMPOUNDS
1) Hydrocarbons are compounds that contain of carbon and hydrogen atoms only (Ex: methane, CH4).
2) Hydrocarbon derivatives are compounds in which one or more hydrogen atoms are replaced by another
nonmetallic atom (Ex: bromomethane, CH3Br).
Aliphatic hydrocarbons consist of carbon atoms bonded together in chain or cyclic (rings) structures of single, double or
triple bonds
H
H
H
H
C
C
C
H
H
H
H
Aromatic hydrocarbons are distinguished by the presence of a special group of six carbons known as the benzene ring.
H
H
H
H
H
H
Classifying Organic Compounds are separated into families and classified according to functional groups. These groups,
the sites where reactions usually take place, help explain the many chemical properties of organic compounds.
3
Functional Group is the characteristic arrangement of atoms within a molecule that determines the most important chemical
and physical properties of the compound.
FAMILY
FUNCTIONAL GROUP
Alkane
-C-C-
Alkene
-C=C-
Alkyne
-C≡C-
Aromatic (Benzene)
Alkanes: General formula : (CnH2n+2)
Alkane: a hydrocarbon that have only single covalent bonds between carbon atoms.
Naming Alkanes
Ex 1: What is the name of the compound with the molecular formula CH4?
Step 1: Use the prefix as the first syllable to indicate the number of carbon atoms in the molecule.
IUPAC (International Union of Pure and Applied Chemistry) prefixes System
MethEthPropButPentHexHeptOct-
Non-
Dec-
1
9
10
2
3
4
5
6
7
8
Step 2: Next, use the ending “ane" to indicate single bonded carbon atoms.
Therefore CH4: -1 carbon, we use ‘Meth”
- single bonds , we use the ending ”ane”
- Methane
Ex 2: Name the following compounds.
A. C3H8
___________________________
C. C5H12
________________
B. C4H10 _____________________
D. C7H16 ______________
Ex 3: Name these continuous-chain hydrocarbons.
A
B.
______________________________
____________________
4
C. C8H18 __________________________________________________________
Homologous series
A group of compounds that change by a constant increment in molecular structure from one compound in the series to
the next
Compounds within a homologous series are known as homologs
Continuous chain alkanes are an example of a homologous series
- The constant increment in alkanes is –CH2- The methane, ethane, propane and butane are an example of a homologous series.
Drawing Structural diagrams
 Determine the # of carbons
 Draw the carbons in a straight line with a line between each carbon.
 Draw a line between the carbon and hydrogen atoms.
Three types of Structural diagrams
1.
Complete structural diagram shows all the atoms and bonds in a structure.
H
2.
H
H
H
C
C
C
H
H
H
H
Condensed Structural Formulas – C-H bonds are omitted but C-C bonds are shown.
For example, the chemical formula of C4H10 can be represented as:
or
or
(dashes are optional)
3.
Line - each end of a line segment represents a carbon atom; hydrogen atoms are not shown
Ex 4: Draw all three-structure diagrams for the following alkanes:
a) C7H16
b) C5H12
Important Fact!
Structural formulas show the bonds in a molecule, but they cannot represent molecules three-dimensionally.
Notice that a carbon "skeleton" is not perfectly straight, but zigzagged. Each carbon atom is bonded to four other
atoms. VSEPR theory predicts that each of the single bonds involving carbon points to a corner of a tetrahedron to
give bond angles of about 109.5°.
5
A really compact way of representing this structure is to use a line structural diagram.
Naming Branched chain alkanes (Alkyl Groups)
Branch – an atom or group of atoms that can take the place of a hydrogen atom on the main carbon chain of
hydrocarbon molecule.
Alkyl group- a hydrocarbon branch that can be one or more carbons long.
-It has one less hydrogen atom than a corresponding alkane.
-Named by removing “ane” and adding –yl.
-It ‘s general formula is CnH2n+1.
- Alkyl groups are examples of substituents: atoms or groups of atoms that replace a hydrogen atom on a chain or
ring of carbon atoms.
Branched chain alkane- alkane with one or more alkyl groups.
Examples of branches:
methyl: -CH3
ethyl: -C2H5 or -CH2CH3
propyl: -C3H7 or -CH2CH2CH3
butyl: -C4H9 or -CH2CH2CH2CH3
pentyl: -C5H11 or -CH2CH2CH2CH2CH3
Naming Branched Alkanes
1.
Find the longest continuous chain of carbons in the molecule and name it.
2.
Number the carbons in the parent chain. Give the branches the lowest number in the chain.
3.
If there is more than one type of alkyl group in the molecule, list their names in alphabetical order.
4.
If an alkyl group occurs more than once, use a Latin prefix to indicate the number present. The Latin prefixes are di
= 2, tri = 3, tetra = 4, penta = 5, and so on.
- e.g. two methyl groups would be represented as dimethyl
5.
Use a number to indicate the location of each alkyl group on the parent chain.
6.
Use proper punctuation: commas are used to separate numbers, and hyphens are used to separate numbers and
letters.
Ex 5: Write a IUPAC name to represent this structural formula.
Ex 6: Write a IUPAC name to represent this structural formula.
Drawing Structural diagram for Branched Alkanes
1.
Draw the parent chain.
2.
Add the alkyl groups (substituents).
3.
Make sure each carbon atom has an octet (e.g. four single covalent bonds).
6
Ex 7: Draw the structural formula for 3-ethyl-2,4-dimethylhexane.
Ex 8: use notebook
Condensed Structural Formulas for Branched Alkanes
Method 1: Draw a condensed parent chain and draw lines to the alkyl substituents.
Method 2: Draw a condensed parent chain and write the formulas for the alkyl substituents in parentheses.
Cycloalkane
A close ring of three or more carbons connected by single bonds is called a cyclic alkane. Cycloalkanes have two less
hydrogen atoms than their corresponding continuous-chain alkanes. The general formula for a cyclic alkane is CnH2n
Ex 9: Draw the full structural formula, condensed structural formula, and line drawing for cyclobutane.
Naming Cyclic Aliphatics
1.
Count the number of carbon atoms in the ring.
2.
Name the structure the same as naming alkane but add the prefix cyclo to the alkane name.
Ex 10: Name this compound
_____________________
Ex 11: Name the cycloalkanes
7
Physical properties of Alkanes
1. Boiling Point
 Relatively low melting and boiling points compared to inorganic compounds of similar size. (why? They have weak
intermolecular force (LDF) holds them together - hydrocarbons are nonpolar)

2.
Q1.
Generally, as the number of carbons atoms in a pure hydrocarbon increases, there is an increase in boiling and
melting points
ALKANES
BOILING POINT
number of electrons
ethane, C2H6
-88.5
18
propane,C3H8
-42.0
26
butane,C4H10
- 0.5
34
pentane, C5H12
36.0
42
Solubility: refers to the ability of a substance to dissolve in a particular solvent.
Alkanes are nonpolar and are soluble in nonpolar solvents only
Q2.
Why does alcohol dissolves in water? Water is polar. It will dissolve polar compounds.
Alcohol is polar. ie: methanol, CH3OH
Why does oil not dissolve in water? Oil is a pure hydrocarbon and like other pure hydrocarbons it is nonpolar. It
will not dissolve in polar water. A common nonpolar solvent used to dissolve some hydrocarbons is carbon
tetrachloride (CCl4 ).
3.
4.
Rotation occurs around the single c-c bonds.
The term saturated refers to organic compounds, which contain single carbon-to-carbon bonds
Structural Isomerism in Alkanes
Structural isomers are compounds have the same molecular formula but different structural formulas
Ex 11: Draw the structural isomers of C4H10.
Ex 12: use notebook
Alkenes (CnH2n)
-Unsaturated compounds - organic compounds that contain double carbon to carbon bonds
Alkynes (CnH2n-2)
-Unsaturated compounds - organic compounds that contain triple carbon to carbon bonds
Rules for Naming Alkenes and Alkynes
Step 1: Find the longest chain that contains the double or triple bonds
Step 2: Number the chain by giving the multiple bond the lowest possible number.
Step 3: Next, use the ending “ene " to indicate a double or “yne” to indicate a triple bond.
Step 4: List and number the alkyl groups present. List them alphabetically.
Step 5: Commas are used to separate numbers, and hyphens are used to separate numbers and letters.
Ex 1: Name the following structure.
8
Ex 2: Name the following structure
_________________
_____________________
__________________
________________________
.
Drawing structural formulas for Alkenes and Alkynes
Step 1: Draw a straight chain containing the number of carbon atoms indicated by the name of the parent carbon chain.
Step 2: Number the carbons atoms in the parent chain from left to right
Step 3: insert the double or triple bond
Step 4: attached all branches
Step5: add enough hydrogen so that all carbons will have four bonds.
Ex 3: Draw the structural formulas for 2-ethyl-1-pentene.
Ex 4: use notebook
Cyclic alkenes (Cycloalkenes) : Rings that possess a double carbon-to-carbon bond.
Ex 5: Draw the full structural formula, condensed structural formula, and line drawing for cyclobutene.
Naming Cyclic alkenes
1.
Count the number of carbon atoms in the ring.
2.
Name the structure the same as naming alkene but add the prefix cyclo to the alkene name.
Ex 6: Name this compound.
Ex 7: Write the possible Structural isomers for following molecular formulas.
a) C4H10
9
b) C4H6 ( seven isomers)
Geometric isomers
Isomers of alkenes that differ only in the arrangement of their substituted groups.
Possible whenever each carbon of the double bond has at least one substituent
- Isomers will differ with respect to their physical and chemical properties.
- Trans - substituted groups on the opposite side of the double bond.
- Cis- substituted groups on the same side of the double bond.
A simple molecular formula for an unsaturated hydrocarbon can result in a large number of isomers, which is one of the
reasons for the tremendous diversity of organic compounds.
Ex 8: Draw structural formulas for and provide names for five of the possible structural isomers of C 6H12.
Physical properties of Alkenes
1. React quickly with small, diatomic molecules (ie hydrogen and halogens)
2. Participates in reaction:
- Addition reactions- converts unsaturated hydrocarbons to saturated hydrocarbons.
-hydrogenation- addition reactions which unsaturated hydrocarbons to saturated ones by the addition of hydrogen
only. It used as starting material in the petrochemical industry for the manufacture of gasoline, plastics, etc
3.
No rotation around carbon-carbon double bond
4.
Alkenes are nonpolar
5.
Alkenes are unsaturated
6.
LDF only
7.
Structural isomers exist for all alkenes larger than propene.
8.
As the number of carbons increase, melting and boiling points increase. Similar melting and boiling points to
alkanes since they only differ by 2 or 4 hydrogen atoms; not a major difference in LDF.
Physical properties of Alkynes
1.
As the number of carbons increase, melting and boiling points increase
2.
Alkynes are nonpolar which are soluble in nonpolar solvents only
3.
LDF only
4.
Alkynes are unsaturated
5.
No rotation around carbon-carbon triple bond
6.
Structural isomers exist for all alkynes larger than propyne.
7.
React in addition and hydrogenation reactions
10
PHYSICAL PROPERTIES OF CYCLOALKANES AND CYCLOALKENES
Cycloalkanes (and cycloalkenes) have higher boiling points and densities than their corresponding alkane (alkene)
with the same number of carbons because of their more compact structure.
ie:
cyclopentane will have a higher boiling point than pentane.
Carbon Range
Boiling Point
State
C1 - C4
-164 to -0.5
gas
C5 - C16
30 to 375
liquid
C17 --->
375 to 515
wax like solid
QUESTION: Construct a table,
a)
list alkene names, boiling points and # of electrons.
b)
c)
2.
ALKENES
BOILING POINT
number of electrons
ethene
-103.9
16
propene
-47.0
24
1-butene
- 6.3
32
1-pentene
30.0
40
list alkyne names, boiling points and # of electrons.
ALKYNES
BOILING POINT
number of electrons
ethyne
-81.8
18
propyne
-23.3
26
1-butyne
- 8.6
34
1-pentyne
40.0
42
for the homologous group with two carbons, listing boiling point and # of electrons
a)
b)
compounds
BOILING POINT
number of electrons
ethane, C2H6
-88.5
18
ethene,C2H4
-103.9
16
ethyne, C2H2
-81.8
14
Which would you predict to have the lower boiling point and why?
Suggest a reason why it does not.
Solution
2. a)
Would predict ethyne having the lowest boiling point since it has the lowest number of electrons therefore the
lowest LDF.
b)
Another factor that affects the strength of LDF is the shape of the molecule. The closer the molecules can get
together the stronger the LDF will be. Ethyne C2H2 is a linear molecule about each carbon.
H-C=C-H
Ethene is trigonal planar about each carbon.
Ethane is tetrahedral about each carbon
11
Aromatic
What is an aromatic compound?
Unsaturated cyclic hydrocarbons
Contain single rings or groups of rings
Simplest aromatic compound is benzene
Aromatic compounds include benzene or are benzene based and have benzene-like structures and properties.
History of Aromatic Hydrocarbons
-Michael Faraday in 1825 determined Benzene’s chemical formula to be C 6H6
-The idea of the benzene structure came to August Kekulé in a dream in 1865.
-Kekulé's ring structure helped explain the unique properties associated with benzene and benzene compounds.
Carbon to Carbon Bonds in Benzene
- 6 carbon atoms ring with a hydrogen bonded to each carbon
- One electron from each carbon is free to participate in a double bond
- To satisfy bonding with the benzene ring is to show the carbons with alternating single and double bonds.
What do you notice about the single and double bonds? Are they the same length?
-Double carbon-to-carbon bonds (134 pm) are 14% shorter than single carbon-to-carbon bonds (148 pm)
-All six carbon-to-carbon bonds in benzene are the same length about 140 pm. (determined by x-ray diffraction)
Unique properties of benzene and other aromatics
-benzene ring is actually a flat hexagonal structure (electrons are delocalized, in other words they not fixed to one carbon but
can move around).
- Bending and twisting of the aromatic molecule would disrupt the electron sharing and the stability of the molecule.
Structure of Benzene
We can draw two structures with the double bonds fore benzene.
H
H
H
H
H
H
Resonance
- Means that there are two or more possible distributions of bonding electrons for a compound.
- Occurs when two or more equal valid structures can be drawn for the molecule.
- The single and double bonds appear to oscillate between two sets of positions.
12
Resonance structure (resonance hybrid) for benzene
This structure represents the resonance that exists in aromatic molecule.
More resonance
- The structure with inserted circle illustrates how electrons can move to form resonance structure, but does not illustrate how
the electrons are involved in bonding.
- Molecules that have resonance are more stable than molecules without resonance. Benzene is not as reactive as a
corresponding six- carbon alkene.
PROPERTIES OF BENZENE
- Molecular formula of benzene, C6H6, is a based on its percent composition and molar mass.
- Melting point = 5.5 oC, boiling point = 80.1 oC which is comparable to the boiling of cyclohexane (81.4 0C).
- Non-polar molecule and is soluble only in nonpolar solvents.
- Benzene has hybrid bonds.
- Benzene is a planar molecule
- Benzene molecules behave like alkanes in chemical reactions, not like the alkenes.
- Benzene molecules do not behave as if they have double bonds.
- Benzene does not undergo addition reaction
Naming Aromatic Hydrocarbons
An alkyl benzene is a compound where one or more hydrogen atoms of a benzene molecule may be replaced with an alkyl
group.
Monosubstituted Benzenes
Compounds containing substituents (ie alkyl group, other atoms) in place of one hydrogen atom are named as derivatives of
benzene.
Naming monosubstituted benzene
Step1: Identify the branch (alkyl or atom) and write it as the first part of the name.
Step2: Complete the name with benzene.
Ex1: Name the compounds
___________________
__________________________
_______________________
Disubstituted Benzenes
Compounds containing substituents (ie alkyl group, other atoms) in place of two hydrogen atoms are named as derivatives
of benzene.
For disubstituted benzenes, there are three possible isomers. The three possible combinations are: 1 and 2, 1 and 3, and 1 and
4. IUPAC (International Union of Pure and Applied Chemistry) recognizes the use of special letter prefixes for disubstituted
benzenes in place of these numbers:
ortho means positions 1 and 2. It is represented by an italicized "o".
meta means positions 1 and 3. It is represented by an italicized "m".
para means positions 1 and 4. It is represented by an italicized "p".
Naming disubstituted benzene
Step1: Give the substituents the lowest possible numbers in alphabetical order.
Step2: write the locations of the branches or use the appropriate classical prefix.
Step3: Complete the name with benzene.
13
Ex 2: Name the compounds.
1,2-dimethylbenzene
ortho-dimethylbenzene
o-dimethylbenzene
1,4-dimethylbenzene
para-dimethylbenzene
p-dimethylbenzene
1,3-dimethylbenzene
meta-dimethylbenzene
m-dimethylbenzene
Ex 3: Provide IUPAC names for following structural formulas.
When Benzene is the Branch (Substituent)
For larger organic molecules, the benzene is considered a branch or an alkyl group. In these cases, there is a long parent chain
and the benzene rings become the branches. As a branch, the benzene ring is called a phenyl group.
Ex 4: Provide IUPAC names for following structural formulas.
Ex 5: Provide IUPAC names for following structural formulas
____________________________
_________________________________
14
Hydrocarbon Derivatives
FAMILY
Alcohols
Carboxylic Acids
FUNCTIONAL GROUP
– OH (R-OH)
Ketones
Ethers
FAMILY
Alkyl Halides
Aldehydes
FUNCTIONAL GROUP
– x x =F, Cl, Br, I (R-x)
Esters
–O –
(R1-O-R2)
Amines
– NH2
(R – NH2)
Amides
Organic Halides (Alkyl Halides):
An organic halide is a compound that contains one or more halogen atoms (F = fluoro, Cl = chloro, Br = bromo, I =iodo) as
part of its molecular structure.
Organic halides have many important uses including: fire retardation, anaesthesia, plastics manufacturing,
refrigeration/cooling systems, etc.
Naming Alkyl Halides
1. Identify and name the longest continuous chain of carbon atoms.
2. Assign lowest possible numbers to the substituents. List the substituents in alphabetical order using appropriate prefixes.
Ex 1: Provide a IUPAC name for each structural formula.
a.
______________________
b.
________________________
c.
_______________________
Ex 2: Write a structural formula for following compounds:
a)
1-chloro-1,2-difluoroethane.
c) 1-chloro-2,2-dimethylpropane
b)
d) 2-methyl- 2,3-dibromopentane
2-chloro-2-methylbutane
15
Alcohols and Ethers
Functional groups - atoms or groups of atoms that give compounds their unique chemical and physical properties.
Alcohols are defined by the functional group called hydroxyl (-OH). The general formula for an alcohol is R-OH where R
represents an alkyl group.
Naming and Drawing Structural Formulas for Alcohols
1.
The -ol suffix in a chemical name identifies a compound as an alcohol; it signals the presence of a hydroxyl group.
2.
Name the longest continuous chain like an alkane then change the -e ending of the alkane name to -ol.
3.
Indicate the location of the hydroxyl group using the lowest possible number. Attach the number to the name with a
hyphen.
4.
If the alkyl group is branched, priority in the numbering of the parent goes to the location of the hydroxyl group.
Ex 1: Write the IUPAC names that correspond to these structural formulas.
a.
___________________
b.
____________________________
c.
d.
_____________________
_______________________
Ex 2: Draw the structural formula and the condensed formula for each alcohol.
a.
2-propanol
b.
3-pentanol
c. 2-methyl-2-butanol
Alcohols: Compounds that possess more than one hydroxyl group are called polyalcohols. An example is a radiator
antifreeze, commonly known as ethylene glycol. Its systematic or IUPAC name is 1,2-enthanediol.
Phenol is an alcohol in which the hydroxyl group is a substituent of a benzene ring
The name consists of the root of the word phenyl (which is used to identify benzene rings) and the suffix ol which represents
a hydroxyl group.
Properties of Alcohols
- A function of the hydrogen bonding associated with the highly polar "OH" bond.
-Short chain alcohols like methanol, ethanol, and propanols have the unique property of being soluble in nonpolar and polar
solvents. This makes them very useful for cleaning oily, greasy, or waxy materials.
-The alkyl component of these alcohols dissolves in nonpolar oils, grease, or wax while the hydroxyl end dissolves easily in
water.
16
-higher melting and boiling points compared to corresponding aliphatic hydrocarbons is due to the strong hydrogen bonds
that form between alcohol molecules and the slightly greater London dispersion forces due to the higher number of electrons
per molecule. For example, ethane boils at -88.5°C whereas ethanol boils at 78.5°C.
Ethers are defined by the functional group known as ether (-O-). The general formula for an ether is R1-O-R2 where R1 and
R2 represent alkyl groups.
In an ether, the alkyl groups can be the same or different. The alkyl groups are methyls (-CH3).
Naming and Drawing Structural Formulas for Ethers
-If they are different, name and list them in alphabetical order as one word, and add the word ether to make a phrase. If they
are the same, add the prefix di- to the alkyl name, and then write the word ether to complete the phrase.
Ex 1: Provide a IUPAC name for each ether.
a.
c.
_________________________
_______ _______________
b.
______________________________.
Ex 2: Draw a structural formula for each ether.
a.
dimethyl ether
b.
butylmethyl ether
Properties of Ethers
- A function of the stable ether link between the alkyl groups.
-Aside from being highly flammable, ethers are generally unreactive.
-Ethers are volatile - they evaporate more easily than alcohols because they lack hydrogen bonding. This property makes
them useful as anaesthetics, propellants (in spray cans), and solvents for varnishes and lacquers.
-Ethers have lower melting and boiling points than their alcohol isomers because they lack hydrogen bonding.
Chemistry, Society and the Environment
-When a car engine doesn't get enough air (oxygen) some gasoline molecules are incompletely burned producing carbon
monoxide, soot, and a rotten egg smell (sulfur compounds).
-The combination of unburned hydrocarbons, sulfur compounds, nitrous oxides, and the other emission products from
automobile engines is responsible for most of the air pollution in large cities like Montreal, Toronto, and Vancouver.
-In many parts of North America, clean air laws are forcing petroleum refiners to make cleaner gasolines. Refiners have
responded by adding alcohols and/or ethers to gasoline. Gasohol, for example, is a blend of 10-15% ethanol and 85-90%
gasoline. Reformulated gasoline (RFG) contains at least 2% tertiary-butylmethyl ether (MTBE).
-MTBE is manufactured by reacting methanol with methylpropene.
17
+
-It's highly branched structure makes it an even-burning fuel that reduces an engine condition called "knock and ping";
however, the main reason it is added to gasoline is because it is an oxygenate.
-MTBE raises the oxygen content of gasoline. Oxygen helps the gasoline to burn more completely thereby reducing harmful
tailpipe emissions such as carbon monoxide.
-The use of MTBE also means less reliance on other octane enhancers like benzene (a known carcinogen) and sulfur
compounds (which when burned contribute to the acid rain problem).
-Most refiners have chosen to use MTBE over other oxygenates primarily for its blending characteristics and for economic
reasons.
-Incomplete combustion of gasoline is more common during the winter. By law, the gasoline supplied to stations in certain
North American cities must be 2.7% oxygen by mass.
-The higher oxygen content results in more complete combustion and less carbon monoxide pollution.
-It is sometimes sold under the marketing slogan "winter gas". Ethanol or MTBE are used to bring the oxygen content of
gasoline up to the legislated levels.
-Because of its solubility in water, MTBE can pass quickly through soil contaminating groundwater. There is substantial
controversy surrounding the use of MTBE because it is a suspected human carcinogen.
-Ethanol, commonly known as grain alcohol is also used as an octane enhancer. It has traditionally been made from the
fermentation of sugars and starches derived from crops like corn.
-It is difficult to achieve high concentrations of ethanol in a fermentation chamber because the yeast that produces it is killed
when the alcohol concentration approaches 15%. Large quantities of grain are needed to produce a relatively small amount of
ethanol.
Aldehydes
Aldehydes have a terminal carbonyl group (-C=O). - that is, the carbonyl group is located at the end of the molecule. The
general formula of an aldehyde is R–CHO where R represents a single hydrogen atom or a chain of carbon atoms .
The simplest aldehyde is methanal, H2CO. The carbon of the carbonyl group is the only carbon atom in the molecule.
Naming Aldehydes
1.
Identify the longest continuous chain of carbon atoms (including the carbon atom in the carbonyl group).
2.
Write the name of the corresponding alkane and replace the -e ending of the alkane name with -al.
Ex 1: Provide a name for each structural formula.
a.
b.
Ex 2: Provide structural formulas for these aldehydes.
a.
Heptanal
b 2-methylbutanal
Ketones
Ketones also contain the functional group called carbonyl (-C=O); however, the carbonyl group in ketones is located on a
non-terminal carbon. This means the simplest possible ketone is propanone: CH 3COCH3.
18
The general formula for ketones is R–CO–R', where R and R' represent alkyl groups. The carbon of the carbonyl group is
counted as part of the carbon chain for naming purposes. The shortest carbon chain in a ketone is three carbons in length.
Naming Ketones
1.
Identify the longest continuous chain of carbon atoms (including the carbon atom in the carbonyl group).
2.
Write the name of the corresponding alkane and replace the -e ending of the alkane name with -one.
3.
If the carbon chain is five carbon atoms or longer, indicate the position of the carbonyl group by assigning it the
lowest number possible.
Ex 1: Provide names for these ketones.
b.
_________________
_____________________.
a.
Ex 2: Provide structural formulas for these ketones.
a.
2- butanone
b.
3-ethyl-4-methyl-2-hexanone
Some Properties and Uses of Aldehydes and Ketones
Many aldehydes and ketones have pleasant odours. For example, benzaldehyde gives almonds their distinctive flavour while
cinnamaldehyde gives the aroma associated with oil of cinnamon. These compounds, like many other aldehydes and ketones,
occur in nature but they may also be synthesized in a lab from alcohols.
Methanal (commonly known as formaldehyde) is by far the most common aldehyde. As formalin (a 40% solution of
methanal and water), it is used as a tissue preservative in biology and hospital laboratories and as embalming fluid in funeral
homes.
Perhaps the most widely recognized ketone is propanone (commonly known as acetone). It is found in substances such as nail
polish remover, varnish, and liquid cleaners. Propanone, like some alcohols, dissolves polar and nonpolar solutes and is
commonly used as a cleaner in organic chemistry laboratories.
Carboxylic Acids
The most familiar with is ethanoic acid which is also known as acetic acid or simply vinegar . They are also called fatty
acids. Fatty acids are long chain hydrocarbons that have a carboxyl group at one end which are found in animal fats and
vegetable oils.
C17H35COOH
The functional group that gives organic acids, also known as carboxylic acids, their chemical and physical properties is the
carboxyl group, -COOH. The general formula for the carboxylic acids is RCOOH where R represents a hydrogen atom or
alkyl group.
Naming Carboxylic Acids
1.
Name the longest continuous chain of carbons, including the carbon of the carboxyl group, using an alkane name.
2.
The carbon atom in the carboxyl group is carbon #1.
3.
Replace the -e ending of the hydrocarbon name with the suffix –oic and add the word acid to the first name to make
a phrase.
19
Ex 1: Provide a IUPAC name for each structural formula.
b.
______________________
______________________________
Ex 2: Draw a structural formula for each carboxylic acid.
a.
butanoic acid
b.
2-methylbutanoic acid
Esters
Esters are abundant in nature. Many of the pleasant odors you associate with flowers and berries are due to esters as are the
scents of bath oils, shampoos, soaps, and room fresheners, artificially flavored ,etc.
The functional group of an ester is
Esters are produced by reacting carboxylic acids with alcohols.
The general formula of an ester is RCOOR' where R represents hydrogen or a carbon chain/alkyl group and R' represents an
alkyl group.
Naming Esters
1.
Count to find the number of carbon atoms in the -OR' component of the structural formula (the part derived from an
alcohol) and assign it an alkyl group name.
2.
Count the number of carbon atoms in the R-C=O component of the structural formula (the part derived from the
carboxylic acid) and assign it an alkane name with an -oate ending in place of the -oic ending. Combine the names
to make a phrase.
Ex 1: Provide a IUPAC name for each structural formula.
b.
_____________________________
______________________.
Ex 2: Provide a structural formula for each ester.
a. butyl ethanoate
b. phenyl ethanoate
Amines
Amines are derived from ammonia (NH3) when more of the hydrogen atoms is replaced by a hydrocarbon group. A nitrogen
atom is the functional group. One hydrocarbon group bonded to an amino group (-NH2). These amines have the general
formula RNH2 where R represents an alkyl group.
To name an amine, identify the alkyl group and add the suffix -amine to its name.
Ex 1: name this structural formula.
________________________
Ex: 2: Draw a structural formula for ethylamine.
20
Amides
The functional group of an amide consists of a carbonyl group and an amino group.
The general formula for an amide is RCONH2 where R represents hydrogen or an alkyl group. To name an amide, write the
name for the carbon chain containing the carbonyl group, drop the -e ending, and add the suffix -amide.
Ex 1: Name this structural formula.
_________________________.
Ex 2: Write a structural formula for propanamide.
Naming Amides with branches
1.
Count to find the number of carbon atoms in the -NR' component of the structural formula (the part derived from an
amine) and assign it an alkyl group name.
2.
Count the number of carbon atoms in the RCO component of the structural formula (the part derived from the
carboxylic acid) and assign it an alkane name, drop the -e ending, and add the suffix -amide. Combine the names to
make a phrase.
Ex 3: Name these structural formulas.
a.
__________________________
Ex 4: Draw the structural formulas.
a. N,N-diethylethanamide
b.
______________________________
b. N,N-ethylmethylethanamide
Amines and amides have unpleasant scents. Urea is one of many common examples.
Amino Acids
Amino acids are the building blocks of proteins. Proteins are the stuff of life!
Substitution
A substitution reaction occurs when a hydrogen atom is removed from a hydrocarbon and replaced by a halide substituent.
When a bromine molecule absorbs energy, the covalent bond is broken resulting in the formation of bromine atoms. These
atoms are good examples of radicals - very unstable and highly reactive particles.
21
Ex 1:
Ex 2:
Ex 3:
Ex4:
Bromine atoms can replace all four of the hydrogen atoms in methane but you will require 4 moles of Br-Br.
Ex 5: Structural isomerism is the existence of two or more structural formulas for one chemical formula.
Ex 6: Draw and name the structural formulas for possible isomeric products of a reaction between propane and two
molecules of chlorine.
Answer Stage 1: The first chlorine molecule reacts with propane.
The products of the first step of the reaction are 1-chloropropane or 2-chloropropane.
Stage 2a: If the second chlorine molecule reacts with 1-chloropropane;
then the possible isomers are: 1,1-dichloropropane, 1,2-dichloropropane, and 1,3-dichloropropane.
Stage 2b: If the second chlorine molecule reacts with 2-chloropropane;
22
then the possible isomers are: 1,2-dichloropropane and 2,2-dichloropropane.
Benzene: Benzene behaves chemically like an alkane (a saturated compound) and not like the alkenes and alkynes
(unsaturated compounds.)
-The hybrid carbon-to-carbon bonds of the benzene ring are very stable and are not easily broken like the double bonds and
triple bonds.
-Since the hybrid bond is not easily broken, reactions between halogens and benzene result in the substitution of hydrogen
with halogen atoms.
Ex 7 : Write an equation using structural formulas to illustrate a reaction between:
a.
benzene and chlorine
b.
one benzene molecule and two chlorine molecules
Ex 8: Write an equation using structural formulas to illustrate a reaction between:
a.
methane and chlorine
b.
Ethane and two moles of iodine
Addition Reactions
Alkenes and alkynes are unsaturated hydrocarbons containing at least one double or triple bond. They do not undergo
substitution reactions; instead, they undergo addition - a reaction in which substituents are added to both carbons involved in
the multiple bond.
23
Alkenes and alkynes are chemically more reactive than alkanes because of the presence of the multiple carbon-to-carbon
bonds. In alkenes, a double bond is reduced to a single bond and in alkynes, a triple bond is reduced to either a double or a
single bond depending on the amount of the substituent available for addition.
Ex 1: Predict the products of addition reactions involving:
a.
ethene and chlorine.
b.
1-butene and chlorine.
c.
cyclohexene and fluorine.
The halogen atoms are added at the location of the double bonded carbon atoms. The reaction is spontaneous unlike
substitution reactions, which require light energy to break the covalent bonds in the diatomic halogen molecules.
Ex 2: Predict the products of addition reactions between:
a.
one molecule of ethyne and one molecule of chlorine
b.
one molecule of ethyne and two molecules of chlorine
Ex 3: Predict the product of a reaction between ethene and hydrogen chloride.
Ex 4: Predict the product of a reaction between ethene and bromine .
Ex 5: Predict the product of a reaction between propene and hydrogen
24
Ex 6: Predict the product of a reaction between ethene and hydrogen bromine
Ex 7: Predict the product of a reaction between ethene and hydrogen
Ex 8: Predict the product of a reaction between ethyne and two hydrogen
Ex 9: Predict the product of a reaction between ethyne and hydrogen
An Application of the Addition Reaction
The decolourization of bromine water is an important test for the presence of a double carbon-to-carbon bond. The
reaction is spontaneous. Bromine, which has a characteristic bright orange color, does not react as easily with saturated
hydrocarbons.
Elimination Reactions: Halogen substituents can be removed from an alkyl halide in a reaction involving a base. The
organic product of an elimination reaction is an unsaturated hydrocarbon.
Ex 1: Write a chemical equation to show the conversion of 2-chlorobutane to an unsaturated hydrocarbon.
25
It removes a hydrogen from either carbon #1 or carbon #3. The hydroxide ion combines with the hydrogen to produce
water, and the eliminated chlorine atom becomes a chloride ion.
Ex 2: Write a chemical equation to show the conversion of 1-bromoethane to an unsaturated hydrocarbon.
Ex 3: Write a chemical equation to show the conversion of 1-chloropropane to an unsaturated hydrocarbon.
Reactions producing Alcohols... Addition Reactions
Ex 1: Predict the product of a reaction between ethane and water
The water molecule splits into hydrogen and a hydroxyl. These species are added to ethene at the location of the double bond.
The product is ethanol. This reaction is an important synthetic source of ethanol.
Ex 2: Predict the product of a reaction between 2-pentene and water
Ex 3: Predict the product of a reaction between ethyne and two moles of water
Ex 4: Predict the product of a reaction between butene and water
Reactions of Alcohols….Elimination Reactions
Alkenes can be produced by elimination of a water molecule from an alcohol. This reaction involves the use of an acid
catalyst. A catalyst is a substance that speeds up a chemical reaction without being consumed. The acid catalyst in the
example below is represented by the symbol H +, (H2SO4)
26
Ex 1:
Predict the product of a reaction between propanol and an acid catalyst.
It should be obvious that a hydroxyl group and a hydrogen atom are being eliminated from the alkyl parent. The result is the
formation of an unsaturated hydrocarbon and water.
Ex 2: Predict the product of a reaction between ethanol and an acid catalyst.
Ex 3: Predict the product of a reaction between cyclohexanol and an acid catalyst
Ex 4: Predict the product of a reaction between 3-pentanol and an acid catalyst
An important application of this reaction type is the ripening of fruit in warehouses. The ripening process is stimulated when
a plant produces ethene. If unripened fruit is stored under the right conditions, the production of ethene is inhibited allowing
for long term storage. In order to initiate the ripening process, the fruit has to be exposed to ethene. This is where an
elimination reaction involving ethanol becomes important.
Reactions producing Esters… Esterification
Esterification: Esters are produced when alcohols and carboxylic acids are reacted in the presence of an
acid catalyst
Ex 1: Predict the product for reaction of methanol and butanoic acid
27
Ex 2: Predict the product for reaction of ethanoic acid and ethanol
Ex 3: Predict the product for reaction of ethanoic acid and 1-butanol
Ex 4: Predict the product for reaction of ethanoic acid and methanol.
Reactions producing Amide
Formation of amide: An amide can be produced by reacting a carboxylic acid with ammonia (NH 3).
Ex 1: Predict the products for reaction of methanoic acid and ammonia
Ex 2: Predict the products for reaction of ethanoic acid and methylamine
Ex 3: Predict the products for reaction of propanoic acid and ethylamine
28
COMMON SOURCES AND USES OF ALKANES
The main source of hydrocarbons is petroleum.
Petroleum refining processes are involved in separation, purification and increasing the yield of the wanted components of
crude petroleum.
Fractional Distillation is the process of separating a number of components (fractions) of a liquid mixture using the fact that
each component will have a different boiling point. It is used in the petroleum industry for separating crude petroleum into a
number of fractions, each containing a large number of compounds with different boiling point.
Modern Fractionation Tower
Crude petroleum is heated to about 400 oC and the vapours pass into the tower. As the vapours pass through the openings in
the trays they condense to the liquid phase. The more volatile portions of the liquid re-vaporize and rise to the next tray.
Thus various components of crude separate themselves.
A
B
C
D
E
F
G
C1 - C5 gaseous fuel for heating homes
C5 - C12 motor gasoline
C12 - C16 kerosene; fuel for diesel and jet engines
C15 - C18 heating oil for furnaces
C16 - C20 lubricating oil
C20 - up paraffin wax
C26 - up asphalt and tars
Combustion Reactions
Hydrocarbons in the range of 7-12 carbons per molecule are the most sought after fractions in crude oil because they
eventually become gasoline. Other hydrocarbons such as kerosene or jet fuel (C14H30) and diesel (C16H34) are also valuable
products of refining because like gasoline they are fuels used in transportation. The most common reaction that these
hydrocarbons undergo is combustion.
When sufficient amounts of oxygen are available, the combustion of hydrocarbons is complete resulting in the production of
carbon dioxide and water vapor. The general form of the equation is:
a hydrocarbon + oxygen gas
carbon dioxide + water vapour
example:
Incomplete Combustion
CxHy + O2(g) → CO2(g) + C(s) + CO(g) + H2O(g)
Ex:
About 90% of the crude oil that enters a refinery exits as gasoline, furnace oil, and jet fuel. The other 10% or so is converted
to hydrocarbons like ethene and styrene - starting materials used in the plastics industry.
Since certain hydrocarbons are in greater demand than others, oil refineries use special processes to convert less valuable
hydrocarbons into more valuable ones. Two of the most important processes used for this purpose are cracking and
reforming.
Cracking produces compounds essential to the plastics and fuels industries. The short chain alkenes are raw materials in the
plastics industry. Longer chain alkenes are used to produce the very valuable branched alkanes that give gasoline a higher
octane rating.
CRACKING
Cracking (Thermal or Catalytic): a process used in the petroleum industry to break down long chain alkanes into smaller
more useful chains. C12 and up are often used as cracking stock.
1)
There is no way to predict the size and type of hydrocarbon.
2)
The process often requires hydrogen as a reactant.
Thermal Cracking:: cracking of a hydrocarbon using heat
29
Catalytic Cracking: cracking of a hydrocarbon using a catalyst
Catalyst: a substance, which helps a chemical reaction, occurs without being used up.
Examples:
a)
The cracking of heptane into propane and butane.
-C-C-C-C-C-C-C- + H2
→
-C-C-C- + -C-C-C-C-
b)
The cracking of 2-methylpentane to produce propane.
CH3
|
-C-C-C-C-C- + H2 → -C-C-C- + -C-C-Cc)
The cracking of 1-butene to produce ethyne and ethane.
-C-C-C=C- → -C ≡ C- + -C-C(don't need to add hydrogen, 2H are removed when the triple bond forms)
d)
The cracking of a hydrocarbon, which produces methane and propane.
-C-C-C-C- + H2
→
-C-
+
-C-C-C-
REFORMING
Reforming (Thermal or Catalytic): a process used in the petroleum industry to convert straight chain alkanes into branched
alkanes having a high octane rating.
1)
two small hydrocarbons make a larger one.
2)
process often produces hydrogen
Examples:
Draw structural diagrams for all organic reactants and products.
a)
Ethane reacts with 2-butene to produce 3-methylpentane
-C-C- + -C-C=C-C- → -C-C-C-C-C|
CH3
b)
Octane is produced from the reaction of hexane and ethane.
-C-C-C-C-C-C- + -C-C-
→
-C-C-C-C-C-C-C-C-
+
H2
c)
2-methylbutane and propane react to for, 3,3-dimethylhexane.
CH3
|
-C-C-C-C- + -C-C-C→ -C-C-C-C-C-C- + H2
|
|
CH3
CH3
Polymers
A polymer is a huge molecule that is formed when hundreds or thousands of small molecules called monomers are bonded
together.
Polymers are literally everywhere. Natural Polymers originate in living things. Examples of natural polymers are cotton,
wool, carbohydrates, proteins, DNA and lipids. The plastic around the screen you are viewing and the plastic that makes up
the mouse you are holding is polystyrene- a synthetic polymer.
Synthetic polymers are things like Dacron, Teflon, nylon, polyvinyl chloride (PVC), polyethylene, polypropylene and
polystyrene. Just think of it - no plastic bags, pipes or containers, no modern carpeting, no high-tech polishes and waxes - the
list is extensive. About half of all synthetic polymers are the products of addition polymerization reactions. Natural polymers
and the remainder of the synthetic polymers are formed by condensation polymerization.
30
Addition Polymerization :is when molecules of the same type of monomer(unsaturated hydrocarbon) are joined together
under specific conditions to form one very long molecule (the polymer). .
About half of all synthetic textile fibres are produced by addition polymerization.
highest temperature
n CH2 = CH2 ---------------> (- CH2 - CH2 ---)n
high pressure
ethylene
monomer
polyethylene (plastics)
polymer
Ex1: Polyvinyl chloride, plastic is the product of the addition polymerization of chloroethene
Ex 2: The addition polymerization of 1,1,2,2-tetrafluoroethene will produce Teflon.
polytetrafluoroethylene
(Teflon-non-stick cooking)
Ex 3: Polymerization of propene (propylene)
Polypropylene (fishing nets)
Condensation Polymerization: involves joining monomers together into a larger molecule called a polymer.
O
||
n (HO-CH2C-OH )
O
O
||
||
.... - O-CH2C-O- CH2C-.....
Esters and amides are produced by condensation reactions. A condensation polymer is the product of condensation chain
reaction. With each monomer that becomes part of the polymer, a by-product molecule is produced. Unlike addition
polymers, which can only grow at one end, a condensation polymer can grow in two or more directions at once.
Here are some examples of molecules involved in condensation polymerization reactions:
What do these molecules have in common? Two active sites or two functional groups. How do they diifer from molecules
that undergo addition polymerization?