Why do primary alkanes/alcohols undergo E2/SN2 while secondary and tertiary undergo E1 and SN1?

Question

aaronq · Answer

steric hindrance

anonymous · Answer

Can you please explain? I havent gotten through that far yet to know what steric hindrance means.

aaronq · Answer

basically physical obstruction. SN2 and E2 are bimolecular meaning that in order for a reaction to take place it needs the reaction of both molecules.
SN1 and E1 are unimolecular, the Carbon is able to polarize due to the near by atoms who "temporarily share" their electrons with that carbon (now a carbocation/carbonium) and render it stable

anonymous · Answer

I still dont understand too much. I mean I can memorize that Sn2 is for primary and methane and Sn1 is for sec/tert, but I dont understand it with words. Is there any way you can draw a picture or something to help me understand? :/

aaronq · Answer

it's easier if i just send you a link to some videos, have you heard of khan academy? http://www.khanacademy.org/science/organic-chemistry/v/comparing-e2-e1-sn2-sn1-reactions

anonymous · Answer

Looking at it right now. Will they talk about steric hindrance and why it goes one way or the other?

it doesnt really explain steric hindrance so far in the one you linked. It did eliminate some possible mechanisms though..

aaronq · Answer

theres a video specifically on steric hindrance on the site, under organic chemistry