hydroxy compounds

Question 1

Reagents and conditions to form alcohols from alkenes

Answer 1

Reagents and conditions: Steam, H3Po4 catalyst, high temperature and pressure

Mechanism: Electrophilic addition

Question 2

Reagents and conditions to form alcohols from halogenoalkanes

Answer 2

Reagents and conditions: Dilute NaOH, warm

Question 3

Reagents and conditions to form primary alcohols from aldehydes

Answer 3

Reagents and conditions: LiAlH4 in dry ether / NaBH4 in methanol / H2, Ni catalyst, room temperature and high pressure

Mechanism: Reduction

Question 4

Reagents and conditions to form secondary alcohols from ketones

Answer 4

Reagents and conditions: LiAlH4 in dry ether / NaBH4 in methanol / H2, Ni catalyst, room temperature and high pressure

Mechanism: Reduction

Question 5

Reagents and conditions to form primary alcohols from carboxylic acids

Answer 5

Reagent and conditions: LiAlH4 in dry ether

Mechanism: Reduction

Question 6

Why are alcohols less acidic than water

Answer 6

Alkyl groups are inductively electron-donating and intensify the negative charge on the alkoxide ion, destabilising the alkoxide ion, causing alcohol to less acidic than water

Question 7

Effects of substituents on acidity of alcohols

Answer 7

Electron withdrawing groups reduces electron density and disperses the negative charge on the alkoxide ion, stabilising the alkoxide ion and causing alcohol to become more acidic

Question 8

Why are pehnols more acidic than alcohols and water

Answer 8

The negative charge in the phenoxide ion will delocalise over the benzene ring, thus stabilising the phenoxide ion and making it a stronger acid than aliphatic alcohols and water

Question 9

Effect of ring substituents on acidity of phenols

Answer 9

1. Electron withdrawing groups -> Ring withdraws more electron density from the oxygen atom and there will be greater delocalisation of the negative charge over the benzene ring, stabilising the phenoxide ion and causing the phenol to become a stronger acid.
2. Electron donating groups -> Ring reduces the delocalisation of negative charge on the oxygen over the ring, destabilising the phenoxide ion and causing phenol to become a weaker acid

Question 10

Reagent and conditions for alcohol to form sodium alkoxide ion

Answer 10

Reagent and conditions: Na(s), Room temperature

Mechanism: Acid-metal reaction

Observations: Rapid effervescence of a hydrogen gas

Question 11

Reagent and conditions for tertiary alcohol to form chloroalkane

Answer 11

Reagent and condition: Concentrated HCl, room temperature

Mechanism: Nucleophilic substitution

Question 12

Reagent and conditions for primary / secondary alcohols to form chloroalkane

Answer 12

Reagents and conditions: Concetrated HCl, ZnCl2, heat

Mechanism: Nucleophilic substitution

Question 13

Reagent and conditions to form bromoalkane

Answer 13

Reagent and conditions:

Concentrated HBr, heat / NaBr, conc H2SO4, heat

Question 14

Reagent and conditions to form halogenoalkanes

Answer 14

Reagent and conditions
To form chloroalkane: PCl3, room temperature
To form bromoalkane: P, Br2, heat
To form iodoalkane: P, I2, heat