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chemistry > Alcohols phenols ethers > Flashcards

Alcohols phenols ethers Flashcards

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1
Q

The bond angle in alcohols is slightly ____ than tetrahedral angle

A

less - due to repulsion between unshared electrons of oxygen

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2
Q

The bond angle in ethers is slightly ____ than tetrahedral angle

A

more - repulsive interaction between bulky R groups

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3
Q

How are alcohols prepared from alkenes

A
  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
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4
Q

How are alcohols prepared from carbonyl compounds?

A
  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
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5
Q

How are alcohols prepared from acids commercially

A

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

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6
Q

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

A

Primary alcohol - aldehyde

Secondary alcohol - Ketone

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7
Q

What is the reaction mechanism from prep from Grignard reagent

A

Nucleophilic addition. hydrolysis

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8
Q

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

A

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

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9
Q

what is another name for phenol

A

carbolic acid

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10
Q

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

A

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

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11
Q

How to prep phenol from chlorobenzene

A

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

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12
Q

How to prep from benzene sulphonic acid

A

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.

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13
Q

How to prep phenol from diazonium salts

A

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

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14
Q

How to prep phenol from cumene

A

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

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15
Q

cumene IUPAC name

A

isopropylbenzene

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16
Q

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

A

intermolecular H-bonding

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17
Q

What id trend of solubility on alcohols and phenols

A

decrease with increase in size

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18
Q

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

A

O-H bond

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19
Q

why are alcohols acidic

A

polar nature oh o-h bond

20
Q

what is the trend of acidic strength on alcohols

A

primary>secondary>tertiary

21
Q

why are alcohols bases

A

presence of unshared electron pairs on oxygen

22
Q

How are esters formed from alcohols and phenols

A

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.

23
Q

What is acetylation

A

introduction of acetyl group (CH3CO) in alcohols and phenols

24
Q

Acetylation of salicylic acid gives what

A

Asprin

25
Q

What is Lucas test

A

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

26
Q

How do alcohols become alkenes

A

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

27
Q

what are the conditions under which alcohols become alkenes

A

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

28
Q

How to isolate aldehyde when prepared from alcohol

A

CrO3 in anhydrous medium is used as the oxidisng agent

29
Q

How to get carboxylic acid directly from alcohoL

A

use strong oxidising agent like potassium permanganate

30
Q

Reagents used when oxidising alcohol

A

aldehyde - PCC, ketone - CrO3

31
Q

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

A

primary becomes aldehyde, secondary becomes ketone, tertiary becomes alkene

32
Q

How to seperate ortho and para nitrophenol

A

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

33
Q

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

A

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

34
Q

how to get better yield of picric acid

A

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

35
Q

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

A

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

36
Q

What is kolbes reaction

A

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

37
Q

What is Reimer Tiemann reaction

A

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

38
Q

How to convert phenol to benzene

A

on heating with zinc dust

39
Q

How to convert phenol to benzoquinone

A

phenol + Na2Cr2O7 and H2SO4

40
Q

How to prep ethers

A

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

41
Q

what is the reaction mechanism for prep of ethers from alcohols

A

SN2

42
Q

Why should we use primary alcohols for prep of ether

A

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

43
Q

Which reactant in Williamson’s synthesis should be primary

A

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

44
Q

How to convert phenol to ether

A

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

45
Q

How to cleave ethers

A

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

46
Q

What ion do you get by protonating anisole

A

oxonium ion C6H5-O(+)H-CH3

chemistry (3 decks)

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