Reaction rate of alcohol?

Question

In the reaction between a hydrohalic acid and alcohol, the rate of reaction depends on the structure of the alcohol, with the third degree being more reactive than the second degree, which is more reactive than first degree alcohols, why will the alcohol strucutre affect the reaction rate in this way?

Answer 1

since the reaction mechanism favors tertiary carbocations more than secondary, and secondary than primary... (in practice primary alcohols take forever and small ones such as methanol cannot use this method at all to become an alkyl halide) because as the post above states, the tertiary carbocation is the most stable

the mechanism:

R-OH + HX the oxygen (electron rich) attracts the H in the acid

the acid dissociates into proton and halide ion... the proton attaches to the oxygen and takes an electron pair, giving oxygen a + formal charge and forming a cation

R-OH2+ + X-

next, water falls off the alcohol molecule, giving a carbocation (this step is the slowest and rate-determining step)

R+ + H2O + X-

then the carbocation attracts the halide ion and they combine into an alkyl halide

RX + H2O

Answer 2

are you referring to a primary, secondary, and tertiary carbon in the alcohol? Assuming you are, the reason is related to the spread of charge, thus stabilizing the molecule. The acid, if stronger than the alcohol, will dissociate the hydrogen from the hydroxyl group leaving a charge on the alcohol. A tertiary carbon can spread this charge about.