YJC 2016 block test
https://www.dropbox.com/s/2lhrq1h7es3o1ly/20160912_194000-1.jpg?dl=0
one part of the question asks for the major product when Br2(aq)
is added to Limonene
is the Major product two OH groups added, because the OH-
nucleophile is in large excess? if it's not the major product, i
dont understand why all the OH- will let the Br- nucleophile attack
the carbonation first, before attacking the carbocation itself?
for the substitution for one Br and one OH, which nucleophile
attack the more stable, tertiary carbocation first? the Answer
given is that the OH is atttached to both the tertiary carbon in
Limonene ,while the Br to the secondary carbon, for the
electrophillic addition of Br2(aq) to the two alkene in
Limonene
if the Answer given is correct, which is OH attach to tertiary
carbon instead of Br, then i don't understand why the remaining of
OH- will let the Br nucleophile attack the secondary carbon,
without attacking the carbocation itself?
U coconaden. U made at least 5 errors here. Still think u're ready
for A grade?
OH- ion is *not* present at all, let alone in large excess.
And the only way u can get 2 OH groups added across a double
bond to generate a vicinal diol is using KMnO4.
Instead of asking "why all the OH- will let the Br-
nucleophile attack the carbonation first, before attacking the
carbocation itself?", u might as well ask "why all the Br-
will let the OH- nucleophile attack the carbonation first, before
attacking the carbocation itself?".
First of all, it's not OH- nucleophile, it's H2O nucleophile.
Secondly, nobody's letting anybody do anything. It's whoever is in
that place at that time with the means, gets there first.
And ur last statement "if the YJC Answer given is correct,
which is OH attach to tertiary carbon instead of Br, then i don't
understand why the remaining of OH- will let the Br nucleophile
attack the secondary carbon, without attacking the carbocation
itself?" shows u're woefully inadequate when it comes to
understanding and drawing mechanisms. The only way u can answer ur
qn is by correctly drawing out the full mechanism. That's something
(if u google out the mechanism and still dun understand it) u'll
need ur school teacher or private tutor to go thru with u
step-by-step.
