Alcohols

Question 1

What is the general formula for alcohols?

Answer 1

CₙH₂ₙ+₁OH

Question 2

What is the functional group for alcohols?

Answer 2

Hydroxyl, -OH group

Question 3

Give the names and chemical formula of the first four members of the Alcohol Homologous series

Answer 3

Methanol CH₃OH

Ethanol CH₃CH₂OH or C₂H₅OH

Propanol C₃H₇OH
isomers:
Propan-1-ol : CH₃CH₂CH₂OH
Propan-2-ol : CH₃CH(OH)CH₃

Butanol C₄H₉OH
isomers:
Butan-1-ol: CH₃CH₂CH₂CH₂OH
Butan-2-ol: CH₃CH₂CH(OH)CH₃

Question 4

What is the main difference in the physical properties between alcohols vs alkenes and alkanes

Answer 4

Alcohols are soluble in water, and have a considerably higher mp and bp as compared to alkanes and alkenes with the same number of carbon atoms [due to the presence of Hydrogen Bonding (not in syllabus but good to know)]

Question 5

What is the trend of solubility of alcohols in water as the number of carbon atoms increases?

Answer 5

Solubility decreases with increasing no. of carbon atoms (as the alkyl chain is insoluble in water)

Question 6

What are the two reactions that alcohols can undergo?

Answer 6

Combustion and Oxidation

Question 7

What are the reagents, conditions and products of the oxidation of alcohols?

Answer 7

Acidified Potassium Manganate (VII) OR Acidified Potassium Dichromate (VI)
Heat

Products: Carboxylic acid + Water

Question 8

What are the products of the Combustion of alcohols?

Answer 8

Carbon Dioxide and Water

Question 9

What are the two (one for combined sci) methods, reagents and conditions needed to produce alcohols?

Answer 9

1. Hydration of Alkenes (Phosphoric (V) acid, 300 Degrees Celsius, 60-70 atm, Steam)
2. Fermentation (yeast, glucose, absence of Oxygen Gas, 37 Degrees Celsius)

Question 10

What are three uses of ethanol, and some examples of those uses?

Answer 10

1. As an organic solvent
   Used as a cleaner, (cleaning laptop screens etc) as it can dissolve molecules that are not soluble in water.

Evaporates quickly, making it suitable for use in deodorants, perfumes etc.

2. As a fuel
   Gasohol is used in some countries as a fuel for motor vehicles

Methylated spirit (mixture of ethanol methanol and water) used in spirit lamps

3. Alcoholic beverages
   Ethanol is the type of alcohol used in alcoholic drinks