IIT JEE , AIEEE Forum - Chemistry , Organic Chemistry

prakhar_galaxy

Sir

well u r also thinking that did i keep on asking problems

Actually i daily get trapped in some ques ,then i discussed them with my sir .The remainig 1 i tried to ask it to u

Coz u tell it with exact mechanism so it makes the problem really clear

now here it is:

umang

In presence of HCOOOH , trans addition of OH takes place
Is this an exception ???

madhusudan.chavan

Per acids act like electrophiles and the reaction is believed to proceed by the electrophilic addition mechanism for C=C.
The peracid would initially form an epoxide; the epoxide ring can be opened by acids or bases to from trans-1,2-diols.
In the acidic medium, the oxygen atom of the epoxide ring gets protonated and the attack of the watermolecule occurs from the side opposite to the oxygen atom to form trans-1,2-diol.
In case of an unsymmetrical epoxides, the attack of nucleophile occurs at the more substituted carbon atom since the +I effect of the alkyl group tends to disperse the +ve charge in the transition state.
Thus in the present case the the OH groups should be trans. Here we have not considered the reaction(if any) of peroxide with carbon carbon triple bond outside the ring.

prakhar_galaxy

Thanx sir

umang

i have a little doubt
does HCOOOH react only with alkenes , and not with alkynes ???
and if with both , then which one to prefer ?

waterdemon

HCOOOH reacts with both Alkene and Alkyne.
Alkene is always prefered if there is no Conjugation with the
functional group.
But if When Alkyne is there and there is formation of trans
OH and a double bond which gets the functional group into
"Resonance".

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Cheers!!!!!!!@@@!!!!!!!!!

umang

i am still confused !
pls explain on the basis of above question
thanks !

waterdemon

Oh ho!!!!!!! dearly sorry yaar !!!!!!!!!

From the above Question.
There will be preference of Alkene over Alkyne.
BcoZ here alkene is outside the ring and the carbon carbon
double bond has got more substituted Carbon than Alkyne.
And the reaction of HCOOOH never takes place with the
Carbon carbon bonds not in the Benzene ring.

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Rate if useful.

Cheers!!!!!!!@@@!!!!!!!!!!

umang

i got it
but there is no benzene ring in the question !!!!
also , shouldnt the addition be anti here (its shown syn) ???

waterdemon

Arey dude,
Benzene ring OR say it cycloHexene.
Cheers!!!!@@@!!!!!

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