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The History of Organic Chemistry
The name organic chemistry came from the word organism. Prior to 1828, all organic compounds had
been obtained from organisms or their remains. The scientific philosophy back then was that the
synthesis of organic compounds could only be produced within living matter while inorganic compounds
were synthesized from non-living matter. A theory known as "Vitalism" stated that a "vital force" from
living organisms was necessary to make an organic compound. 1828, a German chemist Friedrich
Wöhler (1800-1882) amazed the sience community by using the inorganic compound ammonium
cyanate, NH4OCN to synthesize urea, H2NCONH2, an organic substance found in the urine of many
animals. This led to the disappearance of the "Vitalism" theory.
Today, chemists consider organic compounds to be those containing carbon and one or more
other elements, most often hydrogen, oxygen, nitrogen, sulfur, or the halogens, but sometimes
others as well. Organic chemistry is defined as the chemistry of carbon and its compounds.
The Uniqueness of Carbon
There are more carbon compounds than there are compounds of all other elements combined.
Plastics, foods, textiles, and many other common substances contain carbon. With oxygen and a
metallic element, carbon forms many important carbonates, such as calcium carbonate
(limestone) and sodium carbonate (soda). Certain active metals react with it to make industrially
important carbides, such as silicon carbide, an abrasive known as carborundum, and tungsten
carbide, an extremely hard substance used for rock drills and metalworking tools.
The great number of carbon compounds is possible because of the ability of carbon to form
strong covalent bonds to each other while also holding the atoms of other nonmetals strongly.
Carbon atoms have the special property to bond with each other to form chains, ring, spheres,
and tubes. Chains of carbon atoms can be thousands of atoms long, as in polyethylene.
Polyethylene chain:
H H H H H H H H H H H
| | | | | | | | | | |
H-C-C-C-C-C-C-C-C-C-C-C-etc.
| | | | | | | | | | |
H H H H H H H H H H H
Structural Isomers
Isomers are classified as structural isomers, which have the same number of atoms of each
element in them and the same atomic weight but differ in the arrangement of atoms in the
molecule. For example, there ware two compounds with the molecular formula C2H6O. One is
ethanol (also called ethyl alcohol), CH3CH2OH, a colorless liquid alcohol; the other is dimethyl
ether, CH3OCH3, a colorless gaseous ether. Among their different properties, ethanol has a
boiling point of 78.5°C and a freezing point of -117°C; dimethyl ether has a boiling point of 25°C and a freezing point of -138°C. Ethanol and dimethyl ether are isomers because they differ
in the way the atoms are joined together in their molecules.
Aliphatic Hydrocarbons
Hydrocarbons which
do not contain a
benzene ring are
called aliphatic
hydrocarbons. Those
which do contain
benzine are called
aromatic
hydrocarbons.
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Alkanes
Alkanes are a hydrocarbon family that with carbon atoms that are only bonded to each other with single
bonds. Alkanes have the general molecular formula, CnH2n+2, where n = number of carbon atoms in the
alkane molecule. A normal hydrocarbon alkane is one where all the carbon atoms in the molecule are in
a "continuous" chain. A continuous chain does not necessarily mean that the carbons are in a straight
line. The carbons can be in a "zig zag" chain as long as the chain is connected by a carbon atom. The
simplest alkane is methane, CH4. It is made from one carbon atom bonded to four hydrogen atoms. The
table below shows the first ten alkanes.
IUPAC
name
Number of
Molecular Structural
Prefix
Carbons
Formula Formula
Methane 1
Meth- CH4
CH4
Ethane
Eth-
CH3CH3
2
C2H6
Propane 3
Prop- C3H8
CH3CH2CH3
Butane
But-
C4H10
CH3(CH2)2CH3
Pentane 5
Pent- C5H12
CH3(CH2)3CH3
Hexane
Hex-
C6H14
CH3(CH2)4CH3
Heptane 7
Hept- C7H16
CH3(CH2)5CH3
Octane
Oct-
C8H18
CH3(CH2)6CH3
Nonane 9
Non- C9H20
CH3(CH2)7CH3
Decane
Dec-
CH3(CH2)8CH3
4
6
8
10
C10H22
Alkyl Groups
An alkyl is basically an alkane minus one of its hydrogen atoms. For example:
H
H
|
remove one H
|
H-C-H ============> H-C- or
|
|
H
H
methane
methyl
H H
| |
H-C-C-H
| |
H H
ethane
H H
remove one H
| |
============> H-C-C| |
H H
ethyl
CH3-
or
CH3CH2-
Alkyl names are used to name branched alkanes. Any branch in an alkane would be named as the
number of carbons + "yl".
Rules for naming Alkanes
1. First, identify the longest continuous chain in the link of carbon atoms, also known as the parent
chain. The parent chain does not have to be connected in a straight line, it could be in "zig zag"
lines only if it proves to have the most amount of carbon atoms in its chain. Number the carbons
in the parent chain starting from the end closest to the branch(es) so that the substituents will
have the smallest possible numbers.
2. Next, find each alkyl branch and assign it a number according to which carbon atom it is
attached to. The name for the alkyl branch is followed by "-yl" to indicate the number of carbon
atoms are in a branch.
3. List the substituents (with their carbon number) in alphabetical order followed by the name of
the parent alkane. In some cases when there are more than one of a given substituent use the
prefixes di-, tri-, tetra-. Prefixes are not used to determine alphabetical order. The structural
format should look like this: (number of location)-(branch name)(name of parent chain)
4. Use commas between numbers and dashes between numbers and words in naming the IUPAC
formulas. Do not leave spaces in the name.
Cycloalkanes
Cycloalkanes are alkanes in which a bond is formed between the two terminal carbons in the
chain to for a cyclical or ring structure. The prefix cyclo- is written before the name designating
the carbon number in the ring (e.g. cyclohexane).
1. Substituents are named similarly to straight-chained alkanes. The carbons in the ring are
numbered so that the substituents have the smallest numbers.
2. Add the prefix cyclo- to the alkane name
Example:
CH2
/ \
CH2-CH2
cyclopropane
CH2-CH2
|
|
CH2-CH2
cyclobutane
Alkenes
Alkenes are hydrocarbons that contain one or more carbon-carbon double bonds. Alkenes with only one
double bond have the general formula CnH2n
Naming alkenes has the same format as naming alkanes, but be sure to change the -ane ending on
the parent name to -ene ending. This shows that the compound is an alkene.
1. Determine the longest continuous chain of carbons that have the double bond between two of
its carbons. The parent chain must contain the double bond.
2. Number the carbons in the chain so that the double bond would be between the carbons with
the lowest designated number. Numbering could start either from the left end or right end of
the chain. The location of the double bond, not the location of the branches are used for
numbering the alkene.
3. Identify the various branching groups attached to this continuous chain of carbons by name.
4. The format is as follows: (location of branch)-(branch name)(parent chain)
Example:
CH3CH2CH=CH2
4 3 2 1
1-butene
CH3CH=CHCH3
1 2 3 4
2-butene
CH3
CH3
|
|
CH3CH2CHCH2CH=CCH3
7 6 5 4 3 21
2,5-dimethyl-2-heptene
Geometric Isomers
In alkanes, rotational freedom is possible but for alkenes, due to the carbon-carbon double bond, it is
impossible to rotate the bond without breaking it. Geometric isomers are isomers that differ from each
other based on the position of the attached groups relative to the double bond. Two substituents that
are on the same side of the double bond is called cis, meaning "same", two substituents that are on the
same side of the double bond is called trans, meaning "across".
Organic Compounds are categorized by the Functional Groups that
follow below…
Alkynes
Alkynes are hydrocarbons that have at least one triple covalent bond between two carbon atoms. The
general formula for the Alkyne CnH2n-2. Similarly, alkynes are named just like alkenes only with the -yne
ending instead of the -ene ending in naming compounds.
1. Determine the longest continuous chain of carbons that have the triple bond between two of its
carbon atoms.
2. Number the carbons in the chain so that the triple bond would be between the carbons with the
lowest designated number. This means that you have to decide whether to number beginning
on the right end or left end of the chain in order to obtain the smallest possible numbers.
3. Identify the various branching groups attached to this continuous chain of carbons by name.
4. The format is as follows: (location of branch)-(branch name)(parent chain)
Example
Aromatics
Aromatics are carbon compounds that have benzene-like properties. The term "aromatic" came to be
because earlier compounds found with the rings had pleasant fragrances, but it turns out that the ring
has nothing to do with smell. Benzene, back then, had special properties and fascinated scientists for
many years. At last, a structural model was proposed and accepted as the benzene ring. Aromatics
consists of a benzene ring located anywhere within the molecular structure.
If an alkyl group substitutes a hydrogen atom on the benzene ring, the structure is similarly
named like an branched alkane.
1. Obtain the smallest possible numbers to indicate the location of the branched alkanes. In order
to obtain this, numbering starts at one of the substituents and continues either clockwise or
counterclockwise to get the smallest possible numbers. If there is only one substituent,
numbering is not required.
2. Identify the various branching groups attached to this continuous chain of carbons by name.
3. The format is as follows: (location of branch)-(branch name)(parent chain)
If a benzene ring is considered a branch(in larger molecules), then the benzene ring is called a phenyl
group. In this case, the alkane becomes the parent chain and the phenyl thus becomes a branch of the
alkane structure.
Eg. 1-phenylbutane
or
benzene
methylbenzene (toluene)
ethylbenzene
Alcohols
All alcohols contain the hydroxyl functional group, -O-H, attached to single bonded hydrocarbons
(alkanes). Alcohol have the general formula R-OH where R represents any chain of carbon and hydrogen
atoms.
The four most common alcohols are:
CH3OH
methanol
CH3CH2OH
ethanol
CH3CH2CH2OH
1-propanol
OH
|
CH3CHCH3
2-propanol
Alcohols use the same formats as alkanes. To name alcohols,
1. Determine the parent chain. The parent chain must be the longest that includes the carbon
holding the OH group.
2. Number according to the end closest to the -OH group regardless of where alkyl substituents
are.
3. The format is as follows: (location of branch)-(branch name)-(location of OH group)-(parent
chain)
4. Change the parent chain -e ending and replace it with an -ol.
Example:
H
|
H H H-C-H H
| |
|
|
H-C-C---C---C-H
| |
|
|
H O
H
H
|
H
Parent chain: butane
-OH group location: 2
Substituents locations: 3-methyl
Alkane name: 3-methylbutane
Alcohol name: 3-methyl-2-butanol
Alchohols containing more than one hydroxyl group are also called polyalcohols. Polyalcohols
are named similarly to alcohols, with the exception of the prefix di-, tri-, etc before the -ol
ending.
Example:
H H
| |
H-C-C-H
| |
OH OH
1,2-ethanediol
H H H
| | |
H-C-C-C-H
| | |
OH OH OH
1,2,3-propanetriol
Carboxylic Acids
Carboxylic acids is a family of organic compounds that contains the carboxyl group, -COOH. which
consists of a carbon atom joined to an oxygen atom by a double bond and to a hydroxyl group, OH, by a
single bond.
Carboxyl group
1. Determine the parent chain. The parent chain must include the carboxyl carbon.
2. Number starting at the end closest to the carboxyl group.
3. The name of the alkane (parent chain) is changed by replacing the -e with -oic followed by the
word "acid".
Example:
HCOOH
methanoic acid
CH3COOH
CH3CH2CH2COOH
ethanoic acid (acetic acid)
butanoic acid
Esters
Esters are a group of organic compounds with a general formula R1CO2R2 (where R1 and R2 are alkyl
groups) that are formed, along with water, by the reaction of acids and alcohols. Natural occurring
esters of organic acids in fruits and flowers give them their distinctive odors. It also also used for food
aroma and taste, perfumes, synthetic fibres, and solvents.
To name esters,
1. Identify the alkyl group that is attached to the oxygen atom
2. Number according to the end closest to the -CO- group regardless of where alkyl substituents
are.
3. Determine the alkane that links the carbon atoms together. If there is a separation of a
continuous link of carbon atoms due to the oxygen atom, individually name the two alkanes
before and after the oxygen atom. The longer structural alkane is the one that should contain
the carbonyl atom.
4. The format is as follows: (alkane further from carbonyl) (alkane closest to carbony)(parent
chain)
5. Change the parent chain -e ending and replace it with an -oate.
Example:
CH3COOC7H14CH3
octyl ethanoate
Synthesis
The synthesis of aspirin is classified as an esterification reaction. Salicylic acid is treated with
acetic anhydride, an acid derivative, causing a chemical reaction that turns salicylic acid's phenol
group into an acetyl group, (R-OH → R-OCOCH3). This process yields aspirin and acetic acid,
which is considered a byproduct of this reaction. Small amounts of sulfuric acid (and
occasionally phosphoric acid) are almost always used as a catalyst. This method is commonly
employed in undergraduate teaching labs.[58]
Formulations containing high concentrations of aspirin often smell like vinegar.[59] This is
because aspirin can decompose through hydrolysis in moist conditions, yielding salicylic acid
and acetic acid.[60]
The acid dissociation constant (pKa) for acetylsalicylic acid is 3.5 at 25 °C.[61]
Nylon is a thermoplastic silky material, first used commercially in a nylon-bristled toothbrush
(1938), followed more famously by women's stockings ("nylons"; 1940). It is made of repeating
units linked by peptide bonds (another name for amide bonds) and is frequently referred to as
polyamide (PA). Nylon was the first commercially successful synthetic polymer. There are two
common methods of making nylon for fiber applications. In one approach, molecules with an
acid (COOH) group on each end are reacted with molecules containing amine (NH2) groups on
each end. The resulting nylon is named on the basis of the number of carbon atoms separating
the two acid groups and the two amines. These are formed into monomers of intermediate
molecular weight, which are then reacted to form long polymer chains.
Nylon was intended to be a synthetic replacement for silk and substituted for it in many different
products after silk became scarce during World War II. It replaced silk in military applications
such as parachutes and flak vests, and was used in many types of vehicle tires.
Nylon fibers are used in many applications, including fabrics, bridal veils, carpets, musical
strings, and rope.
Solid nylon is used for mechanical parts such as machine screws, gears and other low- to
medium-stress components previously cast in metal. Engineering-grade nylon is processed by
extrusion, casting, and injection molding. Solid nylon is used in hair combs. Type 6/6 Nylon 101
is the most common commercial grade of nylon, and Nylon 6 is the most common commercial
grade of molded nylon. Nylon is available in glass-filled variants which increase structural and
impact strength and rigidity, and molybdenum sulfide-filled variants which increase lubricity.
Aramids are another type of polyamide with quite different chain structures which include
aromatic groups in the main chain. Such polymers make excellent ballistic fibres.