gchem Q

[tRNA]

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if all your given is a primary substrate and a strong base will it undergo SN2 or E2?
plz help thanks

 

[s0chon02]

Sn2 and E2 are both favored by a high concentration of a strong nucleophile.

Sn2= This happens when the nucleophile attacks the carbon that was bearing the leaving group. In order for the nucleophile to do this, the substrate must be unhindered(primary) so the nucleophile can easily approach the carbon.

E2= This happens when the nucleophile attacks a beta hydrogen. Substrates are secondary and tertiary.

Also, increasing temp favors elimination.

Hope this helps!

 

[tRNA]

thanks, got a 2nd Q that i couldn't find in my text,
oxidation of alkylbenzene by KMnO4, ok, lets say u only have a methyl group attached to the benzyl, it will turn to carboxylic acid, no big deal, but what if you have a long chain of alkyl groups attached to the benzylic carbon, after you oxidize that benzylic C to carboxylic acid where do you put the rest of the alkyl chain? do you just eliminate it from the whole thing?

a kaplan question had this type of question, with an ethyl group attached to the benzylic carbon, but when they oxidize it with kmnO4, the product is only a benzoic acid, but where did the rest of the alkyl chain go???

 

[s0chon02]

You can oxidize alkyl groups regardless of their length. It could be (CH2)nCH3, and is oxidized to COOH. The substituent can't be t-butyl though, in this case, no hydrogen atoms. Sorry, i'm not exactly sure on the detailed mechanism behind it.

 

[tRNA]

yea thanks, so no matter how long that alkyl chain is, you just drop the whole thing and put COOH in its place?