17 Hydroxy Compounds

Question 1

Monohydric and polyhydric alcohols

Answer 1

Monohydric: 1 -OH group
Polyhydric: >1 -OH gorup

Question 2

Primary, secondary and tertiary alcohols

Answer 2

Number of R groups attached to the C atom bonded to the -OH group
Primary: 1 R group
Secondary: 2 R groups
Tertiary: 3 R groups

Question 3

Factors affecting boiling point of R-OH

Answer 3

1. Intermolecular hydrogen bonding
2. id-id interactions for increasing C atoms
3. Branching

Question 4

Factors affecting solubility of R-OH

Answer 4

1. Polar -OH group
2. Length of non-polar carbon chain

Question 5

Alkenes, R=R -> Alcohols, R-OH

Answer 5

Electrophilic addition
1. H2O(g), high temp and pressure, H3PO4 catalyst
2. cold conc. H2SO4, heating with H2O

Question 6

Alkyl Halides, R-X -> Alcohols, R-OH

Answer 6

Nucleophilic substitution
NaOH(aq)/KOH(aq), HUR

Question 7

Aldehydes, ketones, carboxylic acids and esters -> Alcohol

Answer 7

LiAlH4 in dry ether

Question 8

Alcohols, R-OH -> Alkenes, R=R

Answer 8

Intermolecular dehydration
1. excess conc H2SO4, heat
2. Al2O3, heat

Question 9

Alcohols, R-OH -> Ether, R-O-R

Answer 9

Intramolecular dehydration
limited conc H2SO4, heat

Question 10

Alcohols, R-OH -> Alkyl Halides, R-X

Answer 10

1. HX (g), heat
2. conc. HCl, ZnCl2 catalyst, HUR
3. PX3, rtp
4. PCl5 (s), rtp
5. SOCl2

Question 11

Alcohols, R-OH -> Esters, R-COO-R

Answer 11

Condensation
1. With R-COOH, few drops of conc. H2SO4, HUR
2. With R-COCl, rtp

Question 12

Alcohols, R-OH -> Aldehydes, R-CHO

Answer 12

Mild oxidation of primary alcohols
acidified K2Cr2O7, heat with immediate distillation

Question 13

Alcohols, R-OH -> Carboxylic acids, R-COOH

Answer 13

Vigorous oxidation of primary alcohols
acidified K2Cr2O7/KMnO4, HUR

Question 14

Alcohols, R-OH -> Ketones R-CO-R

Answer 14

Oxidation of secondary alcohols
acidified K2Cr2O7/KMnO4, HUR

Question 15

Iodoform Test

Answer 15

Warm with I2, NaOH(aq)
Pale yellow ppt of CHI3 formed
CH3CH(OH)R + 4I2 +6OH- -> RCOO- CHI3 + 5I- + 5H2O

Question 16

Reactivity of Phenols, Ar-OH

Answer 16

1. Weaker nucleophile than alcohol
   2.More readily undergoes electrophilic substitutions than benzene
   Due to resonance effect between π electron cloud of benzene and p-orbital of oxygen atom

Question 17

Acidities of Ethanol, Phenol and Ethanoic Acid

Answer 17

Ethanoic acid > Phenol > Ethanoic Acid

Question 18

Factors affecting acidity of Phenol, Ar-OH

Answer 18

Negative charge on oxygen in phenoxide ion delocalises into π electron cloud of benzene ring
Electron donating group destabilises anion, reducing acidity
Electron-withdrawing group stabilises anion, increasing acidity

Question 19

Phenol -> Ester

Answer 19

NaOH (aq), acyl chloride
Phenol must be converted to phenoxide

Question 20

Identification test for phenols

Answer 20

Neutral FeCl3
Violet colouration forms

Question 21

Factors affecting electrophilic substitution of phenols

Answer 21

1. Delocalisation of lone pair electrons on oxygen atom into benzene ring -> increases electrophilic substitution
2. Electronegative O atom decreases electron density in the benzene ring -> decreases electrophilic substitution
   Factor 1»_space;> Factor 2

Question 22

Substitution of BR2 in phenol

Answer 22

1. Br2(aq), rtp -> poly-substitution
2. Br2 in CCl4 -> mono-substitution

Question 23

Nitration of phenol

Answer 23

1. conc HNO3, rtp -> poly-substitution
2. dilute HNO3, rtp -> mono-substitution