10. Hydroxyl derivatives of hydrocarbons - alcohols and phenols

Question 1

Alcohol fermentation

Answer 1

Alcohol fermentation is done by yeast and some kinds of bacteria. These microorganisms convert sugars in ethyl alcohol and carbon dioxide. Alcoholic fermentation begins after glucose enters the cell. The glucose is broken down into pyruvic acid. This pyruvic acid is then converted to CO2, ethanol, and energy for the cell. Humans have long taken advantage of this process in making bread, beer, and wine.

Question 2

Mono- and polihydroxyl alcohols (polyols) – examples

Answer 2

• Compounds that possess more than one alcohol group are called polyhydroxy alcohols.
• Blood sugar is a polyhydroxy compound with 5 alcohol groups. Identify each as primary,secondary or tertiary.
• The alcohols having only one ‘OH’ group are monohydroxy alcohols, as Methanol, Ethanol etc.

Question 3

Characteristics of alcohols - burning

Answer 3

Flammable and readily burn when ignited in air

Question 4

Characteristics of alcohols - oxidizing

Answer 4

Primary alcohols can be oxidized either to aldehydes or to carboxylic acid. Secondary alcohols oxidize to ketone. Tertiary alcohols are resistant to oxidation.

Question 5

Characteristics of alcohols - dehydration

Answer 5

Alcohols are themselves nucleophilic, so R−OH2+ can react with ROH to produce ethers and water in a dehydration reaction, although this reaction is rarely used except in the manufacture of diethyl ether

Question 6

Characteristics of alcohols - reactions with inorganic acids

Answer 6

form esters

Question 7

Characteristics of alcohols - reactions with carboxylic acids

Answer 7

form esters

Question 8

Differentiation between alcohols and phenols

Answer 8

Alcohols

• Alcohols do not have any effect on litmus paper, they are neutral
• They have no action with bromine water
• Develop no characteristic color with neutral FeCl3 solution
• They cannot show coupling reaction with arene diazonium salt
• They do not react with NaOH

Phenols

• They change blue litmus red, they are acidic
• They give white precipitate with bromine water
• Develop characteristic (red, violet, green etc) color with FeCl3 solution
• They form azo-dyes by coupling with arene diazonium salts
• They react with NaOH to form phenoxides