Chemical Reactions of Alcohols and Phenols Flashcards
do alcohols react as nucleophiles or electrophiles
react as both
what happens when alcohol reacts as a nucleophile
O-H bond is broken
what happens when alcohols react as electrophiles
C-O bond is broken(first protonated and then attacked by a nucleophile
What happens when alcohols and phenols react with metals(O-H)
forms alkoxides or phenoxides and hydrogen
why are alcohols and phenols Bronsted acids?
they can donate a proton to a stronger base
order of decreasing acid strength of alcohols
primary>secondary»tertiary
what happens when an electron-releasing group is added
increases electron density on oxygen which decreases polarity of the O-H bond which decreases the acid strength.
which is the weaker acid? alcohols or water?why
alcohols as waters are a better proton donor
which is the stronger proton acceptor? alkoxides or hydroxides
alkoxides. they are stronger bases
why do alcohols acts Bronsted bases
due to the unshared pair of electrons on oxygen, they become proton acceptors.
What happens to the carbon having the hydroxyl group in phenols?
It becomes an electron withdrawing group which makes the oxygen positive.
which reaction indicates that phenols are stronger acids than alcohols and water?
reaction of phenols with aqueous sodium hydroxides
how does the reaction of phenols indicate it is a stronger acid
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.
compare the stabilities of phenoxides and alkoxides
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.
electron-withdrawing groups
nitro, halogens, nitriles
electron donating groups
alkyl groups, alcohols groups and amino groups
how to enhance acidic strength of substituted phenols
presence of nitro groups at ortho and para positions increases delocalisation of negative charge.
why are cresols less acidic than phenols
due to the presence of electron donating group(alkyl group) prevents the formation of phenoxide ion which decreases its acid strength.
what is Esterification
alcohols and phenols react with carboxylic acids, acid chlorides and scid anhydrides to form esters.
what catalyst is used during esterification(carboxylic acid and acid anhydride)
concentrated sulphuric acid
why is water removed as soon as it is formed
because the reaction is reversible
what catalyst is used with acid chlorides and why
pyridine to neutralise HCl which shifts equilibrium to the right side
acetylation of salicyclic acid forms
aspirin
Cleavage of C-O bond is only seen in
alcohols but phenols show with zinc only
