Organic Chemistry

Historically, the term organic chemistry has been associated with the study of

compounds obtained from plants and animals. However, about 175 years ago it was

found that typical organic compounds could be prepared in the laboratory without the use

of any materials derived directly from living organisms. Indeed, today great quantities of

synthetic materials, having properties as desirable as, or more desirable than, those of

natural products, are produced commercially. These materials include fibers, perfumes,

medicines, paints, pigments, rubber, and building materials.

Hydrocarbon Properties

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Parent Names of Unbranched Alkanes

Rules for naming alkanes:

■ Locate the longest continuous chain of carbons. This chain will determine the backbone

or parent name of the molecule.

■ Locate the substituents or side groups attached to the longest chain. Use a prefix to

identify the number of carbons and an-yl suffix to indicate

that the group is a substituent. When two or more of the same substituent is present, use

the prefixes mono–, di–, tri–, tetra–, and so on.

■ Number the longest chain to give the substituents a location number. Use the smallest

possible numbers.

■ Regardless of the location numbers, the substituents are listed alphabetically in the

name. A comma separates numbers, and a dash separates numbers and letters.

Example: Give the IUPAC systematic name for the following molecules:

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Solution:

Locate the longest chain:

Locate the substituents:

Number the chain using the lowest numbers:

Name the molecule:

Other examples:

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Practice

Give the IUPAC systematic name for the following molecules.

Alkenes and Alkynes

The nomenclature of alkenes and alkynes follows the same rules as alkanes, except the

double or triple bond must be numbered. The multiple bond is numbered on the first

number to which it is assigned. Also, because double bonds have a rigid configuration,

they can exhibit a cis or trans isomerism. A cis structure is one with substituents on the

same side of the double bond, and the trans is one with the substituents are on opposite

sides of the double bond.

Example:

Name the following molecules:

Solution:

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Practice

Give the IUPAC systematic name for the following molecules.

Draw the following molecules:

9. trans-3-decene 10. 2-pentyne 11. cis-2-octene

Functional Groups and Some Common Radicals

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Some Common Radicals

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Example:

Identify the functional groups in phenylalanine (an amino acid and component of

aspartame and proteins) and vanillin (vanilla scent):

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Solution:

Practice

Identify the functional groups in the following molecules:

12. Eugenol (spicy fragrance of cloves)

13. Aspirin 14. Cyanoacrylate (“Super Glue”)

ALCOHOLS

Compounds containing the functional group —OH are called alcohols. The —OH group

is covalently bonded to a carbon atom in an alcohol molecule, and the molecules do not

ionize in water solution to give OH− ions. On the contrary, they react with metallic

sodium to liberate hydrogen in a reaction analogous to that of sodium with water.

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Common Alcohols

Isomeric Alcohols

ALDEHYDES AND KETONES

Aldehydes are produced by the mild oxidation of primary alcohols—alcohols with the —

OH group on an end carbon atom.

The mild oxidation of a secondary alcohol (with the —OH group on a carbon atom

connected to two other carbon atoms) produces a ketone.

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Each of these groups is characterized by having a carbonyl group, but the aldehyde has the carbonyl group on one end of the carbon chain, and the ketone has the carbonyl group on a carbon other than one on the end. Acetone is a familar solvent for varnishes and lacquers. As such, it is used as a nail polish remover. The systematic name ending for aldehydes is -al; that for ketones is -one.

ACIDS AND ESTERS

Acids can be produced by the oxidation of aldehydes or primary alcohols. For example,

the souring of wine results from the oxidation of the ethyl alcohol in wine to acetic acid:

A solution of acetic acid formed in this manner is familar as vinegar. The name ending

for organic acids is –oic acid, so the systematic name for acetic acid is ethanoic acid.

Acids react with alcohols to produce esters:

Many simple esters have a pleasant, fruity odor. Indeed, the odors of many fruits and oils

are due to esters. Esters are named by combining the radical name of the alcohol with that

of the negative ion of the acid. The ending -ate replaces the -oic acid of the parent acid.

The ester in the equation above is an example.

Name the following esters:

Ans. (a) Butyl acetate or butyl ethanoate (b) Phenyl formate or phenyl methanoate

The formation of an ester from an alcohol and an acid is an equilibrium reaction. The

reverse reaction can be promoted by removing the acid from the reaction mixture, for

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example, by treating it with NaOH. Animal fats are converted to soaps (fatty acid salts)

and glycerine (a trialcohol) in this manner.

Nitroglycerine, a powerful explosive, is an ester of the inorganic acid HNO3 and glycerol

(glycerine).

AMINESAmines can be considered derivatives of ammonia, NH3, in which one or more hydrogen atoms have been replaced by organic radicals. For example, replacing one hydrogen atom on the nitrogen atom results in a primary amine, RNH2. A secondary amine has a formula of the type R2NH, and a tertiary amine has the formula R3N. Like ammonia, amines react as Brønsted bases:

Aromatic amines are of considerable importance commercially. The simplest aromatic

amine, aniline, C6H5NH2, is used in the production of various dyes and chemicals for

color photography

AMIDES

This class of compounds is formed by the reaction of organic acids with amines. The

functional group and the general formula are

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Any or all of the R groups can be the same or different, and indeed may even be a hydrogen atom. The simplest amide is formamide, HCONH2. The name of each member of the group starts with any radicals attached to the nitrogen atom. Then comes the name of the organic acid, with -oic acid replaced by the word amide.

Amino acids form proteins in the human body with amide linkages, and the same linkages hold together the building blocks of nylon.

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