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Organic Chemistry Lecture Notes
Objectives: After the completion of this chapter you should be able to - a) name hydrocarbons (alkanes,
alkenes, alkynes, aromatics); b) name alcohols, phenols, ethers, and amines; c) name acids, aldehydes,
ketones, and ethers; d) identify alkanes, alkenes, alkynes and aromatics from structural formulas; e)
identify acids, aldehydes, ketones, and esters from structural formulas; f) identify alcohols, phenols, ethers,
and amines from structural formulas; g) identify general formulas of organic compounds; h) answer alcohol
related questions; and i) define/identify miscellaneous terms.
Organic chemistry: (Chemistry of carbon)
The definition of organic chemistry has changed over the years showing the dynamic character of
science. Until the nineteenth century, chemists believed that organic chemicals are related to living
things. This all changed in 1828, when Friedrich Wohler synthesized the organic compound urea (found in
urine) from ammonium cyanate. Organic chemistry is now defined as the chemistry of carbon-containing
compounds.
Carbon atoms are unique in their ability to bond to each other so strongly that they can form long chains,
branches and rings of various sizes. Carbon can also bond strongly to other atoms such as hydrogen,
oxygen, nitrogen, sulfur, and halogens. Carbon forms millions of compounds.
Hydrocarbons:
The simplest organic compounds are hydrocarbons, which contain only hydrogen and
carbon. Hydrocarbons are classified according to the type of bonding between carbon atoms.
Alkanes:
Alkanes contain carbon-to-carbon single bonds only. The general formula is CnH2n+2. Following is a list
of the first ten members that you need to memorize.
Name
Molecular
formula
Condensed structural formula
Methane
CH4
CH4
Ethane
C2H6
CH3–CH3
Propane
C3H8
CH3–CH2–CH3
Butane
C4H10
CH3CH2CH2CH3
Pentane
C5H12
CH3CH2CH2CH2CH3
Hexane
C6H14
CH3CH2CH2CH2CH2CH3
Heptane
C7H16
CH3CH2CH2CH2CH2CH2CH3
Octane
C8H18
CH3CH2CH2CH2CH2CH2CH2CH3
Draw the structural formula
Nonane
C9H20
CH3CH2CH2CH2CH2CH2CH2CH2CH3
Decane
C10H22
CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3
Isomerism:
Isomerism is a very common phenomenon in organic chemistry. Compounds that have the same
molecular but different structural formulas are called isomers. Isomers start to happen from butane which
has only two isomers. Number of isomers increase rapidly with the number of carbon atoms in the chain,
but there is no general formula for prediction. There are three pentanes, five hexanes, nine heptanes. By the
time it reaches 30 carbon atoms in the chain the number of possible isomers are over 4 billion.
Physical and chemical properties of alkanes:
The following Table shows some of the physical properties alkanes. They are nonpolar compounds, do
not dissolve in water. Light alkanes such as those in gasoline (hexane, heptane, octane) dissolve and wash
away body oils when spilled on the skin. Heavier alkanes, when applied on skin, act as emollients
(petroleum jelly).
Cyclic hydrocarbons: (Ring compounds: cycloalkanes, cycloalkenes, cycloalkynes)
Cycloalkanes have a general formula of CnH2n, all carbon being in a closed chain. The simplest member
is cyclopropane.
Name
Structure
Name
Structure
Cyclopropane
or
Cyclobutane
or
Cyclopentane
Cyclohexane
Unsaturated hydrocarbons: (Alkenes - double bond, and alkynes - triple bond)
Alkenes contain at least one carbon-to-carbon double bond (C=C) in the structure. The simplest member
is ethylene, CH2=CH2. Its IUPAC name is ethene. Alkynes contain at least one carbon-to-carbon triple
bond (C≡C). The simplest member is acetylene or ethyne. Unsaturated hydrocarbons undergo addition
reaction. They also form polymers.
Aromatic hydrocarbons: (Benzene, C6H6, and its relatives)
Benzene, has been known to scientists with its molecular formula of C 6H6, which contains a lot of
unsaturation. But these unsaturations do not act as those in an open chain unsaturated hydrocarbon. Kekulé
proposed the ring structure with three alternating double bonds.
Halogenated hydrocarbons: (Remember DDT and PCB? Not such a good friend to the environment.)
One or more hydrogen atoms of a hydrocarbon can be substituted by halogens.
Alkyl groups: Alkanes without one hydrogen. (Remember the stem names?)
Functional groups: (family traits)
Alcohols: (R–OH, only one is drinkable)
When a hydroxyl group (–OH) is substituted for any hydrogen in an alkane, the molecule becomes an
alcohol (R–OH). Methanol (CH3–OH), ethanol (CH3CH2–OH), propanol (CH3CH2CH2–OH), butanol
(CH3CH2CH2CH2–OH) are some earlier members of the series. In the non-IUPAC system these names are
called methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol.
Other names and usage of alcohols:
Multifunctional alcohols - ethylene glycol, glycerol
Phenols: (Not an alcohol. OH is connected to a benzene ring.)
Usage of phenols:
Ethers: (Oxygen between two carbons, R–O–R or R–O–R')
CH3–O–CH3
CH3CH2–O–CH2CH3
CH3–O–CH2CH3
CH3CH2–O–CH2CH2CH3
Usage of ethers:
Aldehydes and ketones: (Formalin and nail polish remover. Carbonyl group is an important part.)
Difference and similarities between aldehydes and ketones - R–CHO and R–CO–R'
Usage of aldehydes and ketones:
Carboxylic acids: (R–COOH, ever tasted vinegar?)
Usage of carboxylic acids:
Esters: (RCOOR', good smelling compounds)
CH3COOCH2CH3
Apricot smell
CH3CH2CH2COOCH2CH2CH2CH2CH3
Usage of esters:
Nitrogen containing organic compounds:
Amines: Organic derivatives of ammonia, NH 3. R–NH2, RR'–NH, RR'R"–N.
Primary amines:
CH3CH2–NH2
Secondary amines:
Tertiary amines:
CH3CH2CH2NH2
Aromatic amine:
Summery table
Compound type
Formula
IUPAC name
Common name
Alkane
CH3-CH3
ethane
ethane
Alkene
CH2=CH2
ethene
ethylene
ethyne
acetylene
Alkyne
Alcohol
CH3CH2OH
ethanol
ethyl alcohol
Aldehyde
CH3COH
ethanal
acetaldehyde
Ketone
propanone
acetone
Carboxylic acid
ethanoic acid
acetic acid
ethylamine
ethyl amine
methyl ethanoate
methyl acetate
dimethyl ether
dimethyl ether
Amine
CH3CH2-NH2
Ester
Ether
CH3-O-CH3
Aromatic hydrocarbon
benzene
benzene
Aromatic acid
benzoic acid
benzoic acid
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