ALCOHOLS, THIOLS, PHENOLS, AND ETHERS

by Marvin B. Gonzaga

ALCOHOLS• contain a hydroxyl group (OH)

attached to an alkyl group • the hydroxyl groups of alcohols

are very polar because of the significant difference between the electronegativities of the oxygen and hydrogen atoms.

Ethanol

• because of intermolecular hydrogen bonding, alcohols boil at much higher temperatures than hydrocarbons of similar molecular weight.

CH3CH2CH2CH3ButaneM.W. = 58

b.p. = -0.5 ℃

CH3CH2CH2OH

1-PropanolM.W. = 60

b.p. = 97.2 ℃

• Alcohols of 1 to 4 carbon atoms are very soluble in water.

• Those with 5 to 6 carbons are moderately soluble in water.

• As the nonpolar, or hydrophobic portion of an alcohol (the C chain) becomes larger relative to the polar, or hydrophobic region (the hydroxyl group), the water solubility of alcohol decreases.

ALCOHOLS

Alcohols of 7 or more C

atoms are nearly insoluble in water.

PHENOLS

• Compounds in which the hydroxyl group is attached to a benzene ring.

• They are polar compounds and are somewhat soluble in water.

• They are found in flavorings and fragrances and are used as preservatives

Mint

PHENOLS

Thymol

PHENOLS

Oregano

Carvacrol

ETHERS

• have the general formula R—O—R• The C—O bonds of ethers are polar.• Do not form hydrogen bonds to one

another because there is no –OH group.• They have much lower boiling points

than alcohols of similar molecular weight but higher boiling points than alkanes of similar molecular weight.

ETHERS

• Diethyl ether was the first general anesthetic used.

• Halogenated ethers are also used as general anesthetics and are less flammable than diethyl ether

Diethyl ether

THIOLS

• Compounds that contain the sulfhydryl group (—SH)

• Similar to alcohols in structure, but oxygen is replaced by sulphur.

• Thiols and many other sulphur compounds have nauseating aromas.

Skunk

Geraniol