chapter 7 Flashcards
what are olefins?
another name for alkenes
what does a carbon-carbon double bond consist of
stable sigma bond and less stable pi bond
unsaturated
capable of adding hydrogen in presence of catalyst
saturated
cannot react with anymore hydrogen
alkane formula
CnH2n+2
alkene or ring formula
CnH2n
formula for degrees of unsaturation
2C + 2 + N - X - H / 2
compound with 2 double bonds =
diene
compound with 3 double bonds =
triene
compound with 4 double bonds =
tetraene
vinyl group
–CH=CH2
allyl group
–CH2–CH=CH2
organic compound produced in the largest volume
ethylene
do boiling points of alkenes increase or decrease with increasing molecular weight
increase
does increased branching of alkenes lead to a higher or lower boiling point
lower
Zaitsev’s rule
alkenes with more highly substituted double bonds are usually more stable
Zaitsev’s product
more substituted alkene
rings that are _____-membered rings or larger can easily accommodate double bonds
five
once a cycloalkane contains at least ____ or more carbon atoms, it can accommodate a trans double bond
8
Bredt’s rule
a bridge bicyclic compound can’t have a double bond at a bridgehead position unless one of the rings contains at least 8 carbons
conjugated double bonds
double bonds that can interact with each other because they are separated by just one single bond
what is the extra stability of the conjugated double bond created by
resonance energy
what does E1 stand for
elimination, unimolecular
the rate limiting transition state of E1 mechanism involves a _______ molecule
single
rate equation of E1
rate = k[RX]
is E1 first or second order
first
what substrate is usually used for E1
tertiary alkyl halide
- can be secondary, but needs stronger conditions and reacts much more slowly
does E1 or E2 form a carbocation
E1
how many steps in E1
2
is the first step of E1 exothermic or endothermic
endothermic
is the second step of E1 exothermic or endothermic
exothermic
is E1 overall exothermic or endothermic
exothermic
does E1 want to use a primary halide
no - needs AgNO3
rate equation of E2 reactions
rate = k[RX][B-]
what does E2 stand for
elimination, bimolecular
how many steps in E2
one
is trans or cis more stable as a product
trans
order of reactivity for E2
3>2>1
bulky bases used for E2
- tBuOK (Na, Li)
- (iPr)2NH
- NEt3
do bulky bases favor SN2 or elimination reactions
elimination
what type of product do bulky bases produce
Hofmann
for an E2 reaction, a _______ arrangement of the orbitals is needed
coplanar
reactions that produce more products than reactants generally increase the _______ of the system
entropy
a decrease in temperature favors
elimination
polar aprotic solvents
- DMSO
- DMF
- CH3CN
- acetone
do polar protic solvents favor elimination or substitution
elimination
reaction with primary alkyl halide
- strong: SN2
- weak: no reaction
reaction with secondary alkyl halide
- strong: SN2, E2
- weak: SN1, E1
reaction with tertiary alkyl halide
- strong: E2
- weak: SN1, E1
catalytic cracking
least expensive way of making alkenes
