106(1) is more acidic because NO2 groups is -I, -R and is present in o-position where -R effect is applicable
and as EWG's increase acidity, hence (1) is more acidic
6 Answers
106
1I am not saying this......
Phenyl will have difficulty in attracting e due to nitro gp. Thus it won't attract e from OH and thus OH bond will not get weaken to become acidic.....
HOPE NOW IT IS CLEAR........
Though I also know that if resonance effect is taken into consideration....THEN NO2 gp. WILL CAUSE -M EFFECT WHILE OH gp WILL CAUSE + M EFFECT.........
THEN WHICH WILL DOMINATE.......SINCE BOTH R OPPOSITE.......???
39If you are talking about where the incoming electrophile will attack, it will be ortho or para to the activator group which is -OH here.
The case here is a little different. Acidity of a phenol is determined by the ease of loss of proton.
In the first substrate, due to chelation/intramolecular H-bonding, the proton is not given away so easily. This decreases acidity(when we compare with p- or m-nitrophenol, that is). This is only the case when -NO2 is at the ortho position wrt -OH.
Had that been a -COOH or similarly strong acidic group instead of -OH, the ortho effect would have overriden intramolecular H-bonding and caused acidity to increase.
More info about the ortho effect : http://answers.yahoo.com/question/index?qid=20071012080118AABWL03
EDIT : I missed one more thing. All nitrophenols are more acidic than phenol. The -I effect of -NO2 contributes to that..
1Which effect dominates of all in mesomeric,hyperconjugative, inductive and electromeric effect.....??
39Hyperconjugation and resonance are close but I've heard that hyperconjugation dominates.
106hmm pritish.. ive read that resonance > hyper > inductive
each can outperform its others if no. of hyper is much more than no. of reso. structures or inductive can overpower others if electronegativity is very high (eg. for F)