Grade 12th passInorganic Chemistry

Q. Why alkyne are more acidic than alkane.please provide correct explanation.

Mohd Mujtaba

8 Years agoGrade 12th pass

4 Answers

Sanjana

Approved Tutor Answer8 Years ago

Recall that, all other things being equal, a hydrogen tends to be more acidic when attached to a more electronegative atom. This is because the conjugate base will be more stable when the negative charge is localized on a more electronegative atom.

Now the reason why alkynes are more acidic than alkenes, which are in turn more acidic than alkanes, is that sp carbon atoms are more electronegative than sp2 carbon atoms, which are in turn more electronegative than sp3 carbon atoms.

The reason for the difference in electronegativity is that p orbitals are on average further away from the nucleus than s orbitals, so the more p-orbital contribution you have to the hybrid orbital, the less electronegative the hybrid orbital. sp orbitals are said to have the greatest "s-character" and sp3 orbitals the least.

Nitesh

Approved Tutor Answer8 Years ago

°/• s character is more in Alkyne than Alkane. We know that s character increases acidity increases .And so due to S- character alkyne has acidic hydrogen.Hence alkyne is more acidic than Alkane.

Puspendu bera

8 Years ago

To give this answer at first we should be a clear idea of the hybridisation for given compound.now we see the appropriate hybridisation of given compound alkanes , alkenes and alkynes.alkanes have sp3 ,alkenes have sp2 ,and alkynes have sp hybridisation , always remember it.actually acidity depends on more characters. Out of these characters, electronegetivity is more important . always remember the order of electronegetivity :sp>sp2>sp3.s orbital is closer to the nucleus than p orobital.so where msurement of s is more there exists more electronegetivity because of s is more attractive to the nucleus than p. Now we calculate the measurements of s character for given compounds . Sp³ has 25%S ,Sp²has 33.33%S and sp has 50% s character . So more s character ,more electronegetivity , sp hybridisation is more electronegetive than sp² which is turn more electronegetive than sp³.so we see that alkynes are more electronegetive than alkenes which turn more electronegetive than alkanes.more electronegetive compound is release H+ easily. So alkynes release H+ easily than alkenes which easily release or donate H+ than alkanes . Thefore alkynes is more acidic than alkenes which is more acidic than alkanes

Yash Chourasiya

5 Years ago

Dear Student

Acidity∝ % s character
% s character is more in Alkyne than Alkane.
So due to S- character alkyne has acidic hydrogen.
Hence alkyne is more acidic than Alkane.

I hope this answer will help you.
Thanks & Regards
Yash Chourasiya