Alkenes: Formation & Properties part two: dehydration & eliminiation reactions

the reactions alcohols undergo depends on the

specific conditions

when assessing alcs pay carfeul attention to

acid type and reaction conditions

secondary/tertiary alcs in HBr/HCL undergo

SN1 reactions

with alcs non-nucleophilic conjugate bases lead to

elimination instead of substitution

dehydration reactions (E1)

require elevated temps

Describe the regioselectivity in elimination (E1)

always consider beta positions in eliminaiton reactions vs alpha positions in subsituiton 

most subsituted alkne

forms preferentially

Zaitsev’s rule

remove hydrogen from carbon with fewest hydrogens to form most stable alkene

zaitsev’s rule forms the most (E1)

thermodynamically stable product

(E1)E-alkenes form preferentially over

Z-alkenes 

E1 mechanism occurs when

sn1 can not proceed

what is the first step in E1

carbocation formation

in E1 mechanism

water acts as elimination base

In e1 rate depends only on

substrate concentration 

reactivity trends in E1 are the

same as sn1 (3>2>1)

E1 can occur with alkyl halids in

weak base/non-nucleophilic solvent

carbocation rearrangements in E1 occur as in SN1 called

hydride/methyl shifts

What are the basic characteristics of E2

rate depends on base and substrate, requires strong base, most eliminiations of alkykl halides go by E2

what are the stereoelectronic requirements of E2

H and leaving group must be anti-coplanar

primary substrate rearrangement in E2

primary alcs can undergo intramolecular hydride shift

kinetic isotope effect

C-D bonds stronger than C-H bonds

eliminiation is 

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