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Alcohols, Phenols and Ethers > Chemical Reactions of Alcohols and Phenols > Flashcards

Chemical Reactions of Alcohols and Phenols Flashcards

1
Q

do alcohols react as nucleophiles or electrophiles

A

react as both

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2
Q

what happens when alcohol reacts as a nucleophile

A

O-H bond is broken

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3
Q

what happens when alcohols react as electrophiles

A

C-O bond is broken(first protonated and then attacked by a nucleophile

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4
Q

What happens when alcohols and phenols react with metals(O-H)

A

forms alkoxides or phenoxides and hydrogen

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5
Q

why are alcohols and phenols Bronsted acids?

A

they can donate a proton to a stronger base

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6
Q

order of decreasing acid strength of alcohols

A

primary>secondary»tertiary

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7
Q

what happens when an electron-releasing group is added

A

increases electron density on oxygen which decreases polarity of the O-H bond which decreases the acid strength.

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8
Q

which is the weaker acid? alcohols or water?why

A

alcohols as waters are a better proton donor

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9
Q

which is the stronger proton acceptor? alkoxides or hydroxides

A

alkoxides. they are stronger bases

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10
Q

why do alcohols acts Bronsted bases

A

due to the unshared pair of electrons on oxygen, they become proton acceptors.

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11
Q

What happens to the carbon having the hydroxyl group in phenols?

A

It becomes an electron withdrawing group which makes the oxygen positive.

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12
Q

which reaction indicates that phenols are stronger acids than alcohols and water?

A

reaction of phenols with aqueous sodium hydroxides

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13
Q

how does the reaction of phenols indicate it is a stronger acid

A

due to the higher eleconegativity of sp2 hybridised carbon of phenol it decreases the electron density on oxygen which increases the polarity increases acid strength.

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14
Q

compare the stabilities of phenoxides and alkoxides

A

the negative charge is localised on oxygen in alkoxides whereas it is delocalised in phenoxides due to resonance(shared by many carbon atoms). due to charge separation by resonance, it makes the phenoxide ion more stable and favours ionisation.

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15
Q

electron-withdrawing groups

A

nitro, halogens, nitriles

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16
Q

electron donating groups

A

alkyl groups, alcohols groups and amino groups

17
Q

how to enhance acidic strength of substituted phenols

A

presence of nitro groups at ortho and para positions increases delocalisation of negative charge.

18
Q

why are cresols less acidic than phenols

A

due to the presence of electron donating group(alkyl group) prevents the formation of phenoxide ion which decreases its acid strength.

19
Q

what is Esterification

A

alcohols and phenols react with carboxylic acids, acid chlorides and scid anhydrides to form esters.

20
Q

what catalyst is used during esterification(carboxylic acid and acid anhydride)

A

concentrated sulphuric acid

21
Q

why is water removed as soon as it is formed

A

because the reaction is reversible

22
Q

what catalyst is used with acid chlorides and why

A

pyridine to neutralise HCl which shifts equilibrium to the right side

23
Q

acetylation of salicyclic acid forms

A

aspirin

24
Q

Cleavage of C-O bond is only seen in

A

alcohols but phenols show with zinc only

25
Q

Reagent used to distinguish classes of alcohols

A

Lucas Reagent

26
Q

Reaction with phosphorus trihalides

A

converted to alkyl bromides by reaction with phosphorus tribromide

27
Q

protic acid

A

concentrated sulfuric acid and phosphoric acid

28
Q

dehydration of alcohols on reacting with what yields

A

yield alcohols on reacting with conc.h2so4 or h3po4

29
Q

dehydration

A

removal of a molecule of water

30
Q

relative ease of dehydration of alcohols(easiest to dehydrate)

A

tertiary>secondary>primary

31
Q

mechanism steps

A

1.protonation(fast)
2.carbocation formastion(slow)
3.elimination of proton

32
Q

oxidation is also called

A

dehydrogenation

33
Q

agent used for yielding aldehyde from oxidation of alcohol

A

pyridine chlorochromate, CrO3

34
Q

agent used for yielding carboxylic acid from oxidation of alcohol

A

potassium permanganate

35
Q

agent used for yielding ketone from oxidation of secondary alcohol

A

CrO3(chromic anhydride)

36
Q

why do tertiary alcohols not undergo oxidation but undergoes dehydration

A

as there are only C-C and C-O bonds and no hydrogens for dehydrogenation

37
Q

dehydration and dehydrogenation difference

A

dehydration- removal of water
dehydrogenation-removal of dihydrogen

Alcohols, Phenols and Ethers (6 decks)

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