13Fr 2) Google helped a bit-
dbts which came to my mind while studying today..
Q1 can conc H3PO4 +conc HNO3 be used as nitrating mixture ??
Q2 we know acetylene is highly acidic...butg it never exists in soln in this form H-C≡C- +H+ ... why ???
Q3 why 2nd step(i.e CH bond breaking step) is rate determining step in sulfonation of benzene though first step has higher activation energy ???
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4 Answers
106Q1. pKa value of H3PO4 is 2.15 as it is a weak acid. while HNO3 is a strong acid.. In nitration, the nitric acid acts as the base (accepts H+ thereby increasing the rate of formation of the nitronium ion) as it is weaker than H2SO4
But in presence of H3PO4 it will act as an acid i.e. donate H+ to form NO3- ion.. Now there is some amount of common ion effect so conc of NO3- will be reduced..
As NO3- can disproportionate (although quite little) to give NO2+ but due to common ion this will be further reduced to become negligible.
Hence NO
Q3. it is a reversible reaction. But I still think first step is rate determining step. Where did you read that?
24thx...
what i read other day was that 2nd step is rate determinin gstep...dont remeber the book name,..becoz read in library