Download CCCH110D Inorganic vs Organic NOTES

The University of Trinidad and Tobago
Course: CCCH 110D
Course Instructors: Balram Mahabir
Centre for Biomedical Engineering
Point Lisas Campus.
Ph: 642-8UTT (8888) ext.: 25096 or 374-8104
Email: [email protected]
THE NATURE OF PROPERTIES OF INORGANIC AND ORGANIC
COMPOUNDS
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ORGANIC VS. INORGANIC
• Organic compounds came from living things vs. Inorganic compounds came from the
earth. Sugar from Cane vs. Salt from oceans
• Organic compounds can be easily decomposed vs. Inorganic Compounds are not easily
decomposed. Burning of Sugar to form CO2 and H2O vs. Extremely high temperatures
required to decompose salt.
• Organic compounds difficult to synthesize in the laboratory vs. inorganic compounds could
be easily synthesized.
• Organic molecules usually are carbon-containing molecules vs. Inorganic molecules may
not contain carbon. NaCl vs. CH4.
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WHY C?
• Carbon, with its 4 valence electrons, can form 4 covalent bonds
When drawing organic compounds remember Carbon always form 4 bonds.
•
Carbon, more than any other element can bond to itself to form chain, branched and ring
structures.
This versatility allows carbon to be the backbone of millions of different
chemical compounds- just what is needed for life to exist.
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ALIPHATIC VS. AROMATIC HYDROCARBONS
Hydrocarbons are organic molecules that consist exclusively, or primarily, of carbon and
hydrogen atoms. There are two (2) types:
• Aliphatic compounds which consists of linear chains of carbon atoms and
• Aromatic compounds which consists of closed rings of carbon atoms.
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HYDROCARBONS
Hydrocarbons are the simplest
organic compounds . Containing only
carbon and hydrogen, they can be
straight-chain, branched chain, or
cyclic molecules. Carbon tends to
form four bonds in a tetrahedral
geometry. Hydrocarbon derivatives
are formed when there is a
substitution of a functional group at
one or more of these positions.
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AROMATIC HYDROCARBONS
The building block of aromatic hydrocarbons is the benzene ring.
The arrangement of atoms is shown below.
The version in the center is often used to
simplify diagrams of molecular structures.
The three double bonds are not restricted to
the positions shown but are free to pass
around the ring. This is sometimes indicated
by drawing the benzene ring as it is on the far
right.
Some examples of biological molecules that
incorporate the benzene ring:
•
•
•
the amino acids tyrosine and phenylalanine
cholesterol and its various derivatives, such as the sex hormones
o estrogens
o testosterone
the herbicide, 2,4-D
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ALIPHATIC HYDROCARBONS
The
simplest
is
methane,
CH4.
Next
is
ethane,
C2H6.
The fatty acids in fats are aliphatic hydrocarbons. If chain holds all the hydrogen atoms it can (i.e. 4
single bonds on all C atoms in the molecule), the molecule is said to be saturated.
If two adjacent carbon atoms each lose a hydrogen atom, a double bond forms between them.
Such a molecule is said to be unsaturated.
Ethene is an example.
H2C=CH2
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NAMES AND FORMULAS OF SOME ORGANIC COMPOUNDS:
Alkanes
CnH2n+2
Alkenes
CnH2n
Alkynes
CnH2n-2
Where n = Number of carbon atoms
These formulas only apply to open-chain (non-cyclical) hydrocarbons.
There are two skills that have to be developed in this area:
•
•
You need to be able to translate the name of an organic compound into its structural
formula.
You need to be able to name a compound from its given formula.
The first of these is more important (and also easier!) than the second. In an exam, if you can't
write a formula for a given compound, you aren't going to know what the examiner is talking about
and could lose lots of marks. However, you might only be asked to write a name for a given
formula once in a whole exam - in which case you only risk 1 mark.
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So, we're going to look mainly at how you decode names and turn them into formulae. In the
process you will also pick up tips about how to produce names yourself.
In the early stages of an organic chemistry course people frequently get confused and daunted by
the names because they try to do too much at once. Just go as far as the compounds you are
interested in at the moment and ignore the rest. Come back to them as they arise during the
natural flow of your course.
CRACKING THE CODE
A modern organic name is simply a code. Each part of the name gives you some useful information
about the compound.
For example, to understand the name 2-methylpropan-1-ol you need to take the name to pieces.
The prop in the middle tells you how many carbon atoms there are in the longest chain (in this
case, 3). The an which follows the "prop" tells you that there aren't any carbon-carbon double
bonds.
The other two parts of the name tell you about interesting things which are happening on the first
and second carbon atom in the chain. Any name you are likely to come across can be broken up in
this same way.
COUNTING THE CARBON ATOMS
You will need to remember the codes for the number of carbon atoms in a chain up to 6 carbons.
There is no easy way around this - you have got to learn them. If you don't do this properly, you
won't be able to name anything!
code
no of carbons
meth
1
Eth
2
prop
3
but
4
pent
5
hex
6
Also Hept – 7; Oct – 8; Non – 9; Dec – 10
IUPAC Rule (International Union for Pure and Applied Chemistry) – in this system, the longest
continuous chain of carbon atoms – called the Base Chain – determines the base name of the
compound.
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Groups of carbon atoms branching off the base chain are called alkyl groups and are names as
substituents. A substituent is simply an atom or group of atoms that has been substituted for a
Hydrogen atom on an organic compound. Common alkyl groups are shown below:
Condensed Structural Formula
Name
- CH3
Methyl
- CH2CH3
Ethyl
- CH2CH2CH3
Propyl
- CH2CH2CH2CH3
Butyl
Refer to Table 18.3
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TYPES OF CARBON-CARBON BONDS
Whether or not the compound contains a carbon-carbon double bond is shown by the two letters
immediately after the code for the chain length.
code
Means
an
only carbon-carbon single bonds
en
contains a carbon-carbon double bond
For example, butane means four carbons in a chain with no double bond.
Propene means three carbons in a chain with a double bond between two of the carbons.
Alkyl groups
Compounds like methane, CH4, and ethane, CH3CH3, are members of a family of compounds
called alkanes. If you remove a hydrogen atom from one of these you get an alkyl group.
For example:
•
•
A methyl group is CH3.
An ethyl group is CH3CH2.
These groups must, of course, always be attached to something else.
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ISOMERS: What are isomers?
•
Isomers are molecules that have the same molecular formula, but have a different
arrangement of the atoms in space. That excludes any different arrangements which are
simply due to the molecule rotating as a whole, or rotating about particular bonds.
What is Structural Isomerism?
Types of Structural Isomerism:
1. Chain isomerism
These isomers arise because of the possibility of branching in carbon chains. For example, there
are two isomers of butane, C4H10. In one of them, the carbon atoms lie in a "straight chain"
whereas in the other the chain is branched.
.
Be careful not to draw "false" isomers which are just twisted versions of the original molecule. For
example, this structure is just the straight chain version of butane rotated
about
the central carbon-carbon bond.
2. Position isomerism
In position isomerism, the basic carbon skeleton remains unchanged, but important groups are
moved around on that skeleton.
For example, there are two structural isomers with the molecular formula C3H7Br. In one of them
the bromine atom is on the end of the chain, whereas in the other it's attached in the middle.
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If you made a model, there is no way that you could twist one molecule to turn it into the other one.
You would have to break the bromine off the end and re-attach it in the middle. At the same time,
you would have to move a hydrogen from the middle to the end.
Another similar example occurs in alcohols such as C4H9OH
These are the only two possibilities provided you keep to a four carbon chain, but there is no
reason why you should do that. You can easily have a mixture of chain isomerism and position
isomerism - you aren't restricted to one or the other.
So two other isomers of butanol are:
3. Functional group isomerism
In this variety of structural isomerism, the isomers contain different functional groups - that is, they
belong to different families of compounds (different homologous series).
For example, a molecular formula C3H6O could be either propanal (an aldehyde) or propanone (a
ketone).
There are other possibilities as well for this same molecular formula - for example, you could have
a carbon-carbon double bond (an alkene) and an -OH group (an alcohol) in the same molecule.
Another common example is illustrated by the molecular formula C3H6O2. Amongst the several
structural isomers of this are propanoic acid (a carboxylic acid) and methyl ethanoate (an ester).
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Some common functional groups are given in the table below.
Common Functional Groups
Functional Group Name
F, Cl, Br, or I
Example
Alkane
CH3CH2CH3 (propane)
Alkene
Alkyne
Alkyl halide
Alcohol
Ether
Amine
CH3CH=CH2 (propene)
CH3CCH (propyne)
CH3Br (methyl bromide)
CH3CH2OH (ethanol)
CH3OCH3 (dimethyl ether)
CH3NH2 (methyl amine)
The C=O group plays a particularly important role in organic chemistry. This group is called a
carbonyl and some of the functional groups based on a carbonyl are shown in the table below.
Functional Groups That Contain a Carbonyl
Functional Group Name
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Example
Aldehyde
CH3CHO (acetaldehyde)
Ketone
CH3COCH3 (acetone)
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Acyl chloride
CH3COCl (acetyl chloride)
Carboxylic acid CH3CO2H (acetic acid)
Ester
CH3CO2CH3 (methyl acetate)
Amide
CH3NH2 (acetamide)
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HYDROCARBON REACTIONS:
1. Combustion Reactions:
Hydrocarbons (alkanes, alkenes and alkynes) all undergo Combustion. In a combustion
reaction, the hydrocarbon reacts with oxygen to form carbon dioxide and water.
Refer to examples in Chapter 18.
Hydrocarbon combustion reactions are highly exothermic – they emit large amounts of
heat. This heat can be used to warm homes and buildings etc.
2. Substitution Reactions:
Alkanes undergo substitution reactions, in which one or more hydrogen atoms on an
alkane are replaced by one or more other atoms. For example halogen (F, Cl, Br, I)
substitution.
Refer to examples in Chapter 18.
3. Addition Reactions :
Alkenes and Alkynes undergo addition reactions in which atoms add across the multiple
bonds. For example the addition of chlorine converts the carbon carbon double bond into
a single bond because each carbon atom now has a new bond to a chlorine atom.
Alkenes and Alkynes can also add hydrogen in hydrogenation reactions in the presence of
an appropriate catalyst.
Refer to examples in Chapter 18.
TO SUMMARIZE:
 All hydrocarbons undergo combustion reactions.
 Alkanes undergo substitution reactions.
 Alkenes and Alkynes undergo addition reactions.
4. Elimination :
5. Esterification :
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Alcohols react with carboxylic acids in the presence of catalytic amounts of a strong
inorganic acid, such as H2SO4 or HCl, to give esters and water, a process called
esterification.
Eg acetic acid (ethanoic acid) and ethanol to give ethyl acetate and water
(draw out structures)
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MONOMERS, POLYMERS AND POLYMERIZATION.
 Polymers are long chainlike molecules composed of repeating units.
 The individual repeating units are called monomers.
 Naturally occurring polymers include starches, proteins and Deoxyribonucleic Acid (DNA)
while Synthetic polymers compose many frequently-encountered plastic products such as
PVC tubing, Styrofoam products, nylon and plexiglass.
 Addition polymer – polymer in which the monomers simply link together without the
elimination of any atoms (e.g. polyethylene), Condensation polymer – polymer that
eliminate an atom or a small group of atoms during polymerization.
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HYDROCARBON CRACKING VS. HYDROCARBON REFORMING

Hydrocarbon Cracking :
Breaking an alkane down into smaller fragments is known as Cracking. When a mixture
of alkanes from the gas oil (C12 and higher) fraction are heated at very high temperatures
( approx 500 degrees Celsius) in the presence of a variety of catalysts, the molecules
break apart and rearrange to smaller, more highly branched alkanes containing 5 to 10
carbons. This process is called catalytic cracking. Cracking can also be done in the
absence of a catalyst – called thermal cracking – but in this process the products tend to
have unbranched chains, and alkanes with unbranched chains have a very low “octane
rating”. Such processes are important in the oil – refining industry for the production of
gasoline and other liquid fuels from petroleum.

Reforming :
Another process converts alkanes into aromatic hydrocarbons with approx. the same
number of carbon atoms. The aromatics are highly efficient fuels and are used as
feedstocks for the chemical industry. Because the process reforms a new hydrocarbon
from an old one, it is referred to as Reforming. An example of reforming is the conversion
of heptane into methylbenzene (toluene).
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TYPICAL FRACTIONS OBTAINED BY DISTILLATION OF PETROLEUM.
Boiling range of fraction
(degrees Celsius)
Below 20 degrees
20 – 60 degrees
Number of carbon atoms per Uses
molecule
C1 – C4
Natural gas, bottled gas,
petrochemicals.
C5 – C6
Petroleum ether, solvents
60 – 100 degrees
C6 – C7
Ligroin, solvents
40 – 200 degrees
C5 – C10
Straight – run Gasoline.
175 – 325 degrees
C12 – C18
Kerosene and Jet fuel.
250 – 400 degrees
C12 and higher
Gas oil, fuel oil and diesel oil
Nonvolatile liquids
C20 and higher
Nonvolatile solids
C20 and higher
Refined mineral oil, lubricating
oil and grease.
Paraffin wax, asphalt and tar
Reference:
Tro, N. J (2004). Introductory Chemistry. (H. K. P., Ed.) USA: Pearson Education, Inc:
Chapter 18.
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