[carboneel]

let me set up the situation first

RXN 1:  POCl₃ plus cyclohexanol in pyridine @ 0 degrees celcius yields 1-cyclohexene (via E2)

RXN 2:  PCl₃ plus cyclohexanol in pyridine when heated yields 1-chloro cyclohexane (via Sn2)

here's a few quick questions i suppose,

why in reaction 1 at 0 degrees, is the elimination product formed (the alkene) when the temperature should favor the substitution product (the alkyl chloride)?

Why in reaction 2 when heated, the substitution product is formed (the alkyl chloride)? again with the question in mind, why isn't the elimination product formed as it should be favored by the high temperature?

and the more important questions and the one my professor and i want to look into, why ISN'T the substitution product formed in the first reaction? it has the lower temperature (which should favor substitution over elimination) and in both mixtures, chloride ion in present (from being displaced for the P in both cases to form the intermediate) and why ISN'T the elimination product formed in the solution that was heated?

if you have any empirical data to show why these reactions behave the way they do, please provide as much information as you can, sparing no information that seems above my level of knowledge. (if i don't know what you're saying or what you mean, i'll look it up, ask professors and get involved more as this is pretty interesting to me)

and lastly, if there has been nothing to show why this is, don't steal my undergrad research idea as this is something i'd like to do to get my BS in Chem. 

thanks for any input/insight,
-Erich