Question

Explain what happens when with equation but-2-ol is treated with conc h2so4 at 140c

Answer 1

HERE IS YOUR ANSWER ...


1-butene I believe is the major product. (oh, sorry, new IUPAC calls it but-1-ene!)


CH3COHCH2CH3 --> H+, heat --> dehydration reaction CH3CxCH2CH3 + H-OH (x = empty bond on that carbon). Rearrangement occurs thru inductive effect, and the CH3 on the end (C1) lends an H to C2 to stabilize it's tetrahedral structure.



Now you have...--> CH2=CHCH2CH3, but-1-ene. Since there are more H's on the C with the double bond, they call this a ZAITZEV product (or a product where the reaction follows Zaitzev's rule).





A minor product would be but-2-ene (CH3CH=CHCH3), where, after the dehydration reaction, extra H+ from the acid adds via MARKOVNIKOV's rule, which states that in an addition, H will add to the C with the most H. In this reaction, there are 2 possibilities -- trans-but-2-ene and cis-but-2-ene. CIS means the 2 hydrogens are on the same side of the molecule, leading to steric hindrence; TRANS means 1 H is on the top and one is one the bottom, not sterically hindered.


CIS but-2-ene

.........H..H
CH3-C=C-CH3

TRANS but-2-ene

.........H
CH3-C=C-CH3
..............H





HOPE IT HELPS YOU! !!!