Alcohols phenols ethers

Question 1

The bond angle in alcohols is slightly ____ than tetrahedral angle

Answer 1

less - due to repulsion between unshared electrons of oxygen

Question 2

The bond angle in ethers is slightly ____ than tetrahedral angle

Answer 2

more - repulsive interaction between bulky R groups

Question 3

How are alcohols prepared from alkenes

Answer 3

1. acid catalysed hydration - alkenes react with water in presence of acid as a catalyst. MKR
2. hydroboration oxidation - diborane + alkenes give trialkyl borane which on reaction with hydrogen peroxide in the presence of aq NaOH gives alcohol. AMKR

Question 4

How are alcohols prepared from carbonyl compounds?

Answer 4

1. Reduction of aldehydes and ketones - addition of H2 in presence of catalyst - Pd Pt Ni NaBH4 LiAlH4
2. Reduction of carboxylic acid - reduced to primary alcohol with excellent yield by LiAlH4

Question 5

How are alcohols prepared from acids commercially

Answer 5

Converting to esters by adding R’OH in acid presence and then converting ester to alcohol by catalytic hydrogenation. (H in presence of catalyst)

Question 6

What type of alcohol do aldehyde and ketone give on reduction?

Answer 6

Primary alcohol - aldehyde

Secondary alcohol - Ketone

Question 7

What is the reaction mechanism from prep from Grignard reagent

Answer 7

Nucleophilic addition. hydrolysis

Question 8

What type of alcohols are produced when we use Grignards reagent to prepare them

Answer 8

primary alcohol - methanal
secondary alcohol - aldehydes
tertiary alcohol - ketones

Question 9

what is another name for phenol

Answer 9

carbolic acid

Question 10

Name the 4 methods that can be used to prepare phenol in the lab

Answer 10

From haloarenes, From benzene sulphonic acid, From diazonium salts, From cumene

Question 11

How to prep phenol from chlorobenzene

Answer 11

Chlorobenzene fused with NaOH at 623K and 320 atm gives sodium phenoxide. On acidification with HCl gives phenol

Question 12

How to prep from benzene sulphonic acid

Answer 12

Benzene is sulphonated with oleum and benzene sulphonic acid so formed is converted to sodium phenoxide on heating with molten sodium hydroxide. Acidification of sodium salt gives phenol.

Question 13

How to prep phenol from diazonium salts

Answer 13

amine + NaNO2 + HCl at 273-278 K gives diazonium salt. Diazonium salts are hydrolysed to phenols by warming with water or treating with dilute acids

Question 14

How to prep phenol from cumene

Answer 14

Cumene oxidised in presence of air to cumene hydroperoxide. converted to phenol and acetone by treating with dilute acid.

Question 15

cumene IUPAC name

Answer 15

isopropylbenzene

Question 16

Why is bp of alcohols and phenols higher than other classes of compounds

Answer 16

intermolecular H-bonding

Question 17

What id trend of solubility on alcohols and phenols

Answer 17

decrease with increase in size

Question 18

Which bond has to break on alcohols from them to act as nucleophiles

Answer 18

O-H bond

Question 19

why are alcohols acidic

Answer 19

polar nature oh o-h bond

Question 20

what is the trend of acidic strength on alcohols

Answer 20

primary>secondary>tertiary

Question 21

why are alcohols bases

Answer 21

presence of unshared electron pairs on oxygen

Question 22

How are esters formed from alcohols and phenols

Answer 22

Carboxylic acid/acid anhydride: conc H2SO4, reversible, ROH +R’COOH = ROCOR’ +H20. water is removed as soon as it is formed.
Acid chloride: presence of base (pyridine) to neutralise HCl formed.

Question 23

What is acetylation

Answer 23

introduction of acetyl group (CH3CO) in alcohols and phenols

Question 24

Acetylation of salicylic acid gives what

Answer 24

Asprin

Question 25

What is Lucas test

Answer 25

Tertiary halides from alcohol - turbidity immediately (white ppt) Secondary alcohols - turbidity after a few minutes Primary alcohol - no turbidity at room temp

Question 26

How do alcohols become alkenes

Answer 26

dehydration in presence of protic acids (H2SO4, H3PO4) or catalysts such as anhy ZnCl2, alumina

Question 27

what are the conditions under which alcohols become alkenes

Answer 27

ethanol - H2SO4 ,443K 2-propanol - 85% H3PO4, 440K tertiary - 20% H3PO4, 358K

Question 28

How to isolate aldehyde when prepared from alcohol

Answer 28

CrO3 in anhydrous medium is used as the oxidisng agent

Question 29

How to get carboxylic acid directly from alcohoL

Answer 29

use strong oxidising agent like potassium permanganate

Question 30

Reagents used when oxidising alcohol

Answer 30

aldehyde - PCC, ketone - CrO3

Question 31

what happens when we pass vapours of primary or secondary alcohol over heated copper at 573 K

Answer 31

primary becomes aldehyde, secondary becomes ketone, tertiary becomes alkene

Question 32

How to seperate ortho and para nitrophenol

Answer 32

steam distillation. o is steam volatile due to intramolecular hydrogen bonding and p is less volatile due to intermolecular hydrogen bonding

Question 33

What different products are obtained when we use dil HNO3 and conc HNO3 with phenol

Answer 33

dil - nitophenol , conc - picric acid (2,4,6 - Trinitrophenol)

Question 34

how to get better yield of picric acid

Answer 34

treat phenol with conc H2SO4 first to get 2,4 - disulphonic acid and then conc HNO3

Question 35

What are the different products we get on treating phenol with bromine in different conditions

Answer 35

in solvents with low polarity like CHCl3 or CS2 and at low temp - monobromophenols with bromine water - 2,4,6-tribromophenol as white ppt

Question 36

What is kolbes reaction

Answer 36

when phenol is treated with NaOH it becomes phenoxide ion which is even more reactive. The ion + CO2 and acid gives 2- Hydroxybenzoic acid / salicylic acid

Question 37

What is Reimer Tiemann reaction

Answer 37

Phenol + CHCl3 +NaOH gives intermediate benzal chloride. On treating with alkali we get salicylaldehyde

Question 38

How to convert phenol to benzene

Answer 38

on heating with zinc dust

Question 39

How to convert phenol to benzoquinone

Answer 39

phenol + Na2Cr2O7 and H2SO4

Question 40

How to prep ethers

Answer 40

dehydration of alcohol-protic acid (413K for ethanol to ethoxyethane) Williamson synthesis - alkyl halide + sodium alkoxide

Question 41

what is the reaction mechanism for prep of ethers from alcohols

Answer 41

SN2

Question 42

Why should we use primary alcohols for prep of ether

Answer 42

secondary and tertiary will follow SN1 rxn but elimination competes over substitution forming alkenes

Question 43

Which reactant in Williamson's synthesis should be primary

Answer 43

Alkyl halide should be primary else elimination will happen. It follows Sn2 mechanism. Sodium alkoxide can be tertiary

Question 44

How to convert phenol to ether

Answer 44

Williamson's synthesis. Add NaOH to give phenoxide ion and then add R-X

Question 45

How to cleave ethers

Answer 45

drastic conditions with excess of H-X where x = I, Br

Question 46

What ion do you get by protonating anisole

Answer 46

oxonium ion C6H5-O(+)H-CH3