1. Aldehydes and ketones undergo nucleophilic addition. In this case more the (i.e. addition of HCN) +1 effect of the R-group and more the steric hindrace, lesser is the reactivity therefore, their increasing order of reactivity is Di - tert - butyl ketone < Methyl tert butyl ketone < Acetone < Acetaldehyde.
2. In carboxylic acids +1 effect of R group decreases and -I effect of halogen increases the acidic character. Further, nearer the halogen atom to the carboxylic acid group, stronger is its -I effect. Therefore, the increasing order of acid strength is
(CH3)2CH-COOH < CH3-CH2– CH2– COOH < CH3– CH (Br) CH2COOH < CH3CH2-CH(Br) COOH
3. In benzoic acid and its derivatives, electron withdrawing group attached to ring increases its acidic strength while electron releasing group decreases the acidic strength. The effect is more pronounced if such a group is present at p-position.
Nitro group is electron withdrawing (‘R effect) while methoxy group in an electron releasing. There fore increasing order of acid strength is
4 methoxy benzoic acid < Benzoic acid
< 4 - Nitrobenzoic acid <3, 4- Dinitro benzoic acid.