Glossary of MCAT organic chemistry chapter 5 alkenes alkynes

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general formula for alkene is?
degree of unsaturation means?
how many double bonds it has
N=1/2(2n + 2-m) is used to determ?
the degree of unsaturation
what formula do use to determ degr of unsat?
N=1/2(2n + 2-m)

based on molec CnHm
alkenes are ______________ react than alkanes
alkenes are also called?
what terms can you use to describe alkenes?
cis, trans, e and z
ethylene is?
propylene is
2 methyl 1 - propene is?
mp and bp of alkenes?
incr w incr molec weight
trans alkenes have ________ mp than cis alkenes
why do trans alkenes have higher mp than cis?
they are more symmetr
trans are less __________ than cis alkenes
cis alkenes have higher bp than trans alkenes due to>?
in an alkene the _____________ is electroneg and the ________ are electropo
double bond is electroneg
alkyl gr are electropos
in trans 2 -butene the dipole moments?
cancel each other out
t or f
cis 2-butene has a net dipole moment
synth of alkenes
most common way of synth?
elimination react
of alc or alkyl halides
what 2 things are commonly elimin to make alkenes?
1. alc
2. alkyl halides
form alkenes you lose?
1. HX
2. H2O
eliminat occurs by either?
E1 proc thr a ?
carbocat intermediate
E1 the carbocation is a
a. intermed
b. transition state
a. intermed
E1 rate of react is depend on?
descr 2 steps of E1?
1. leav gr leaves, carbocat is formed
2. proton is remov by base
E1 is favored by?
highly polar solv
branch carbon ch
good leav gr
weak nucleph in low concentr
What mech is competit with E1?
E1 and Sn1 are similar in that?
they are favor by the same factors
T or F
low temperat favor E1
High or low temper
which favor E1
high temperatures
E2 occurs in how many steps?
E2 rate is depend on?
concentr of substr and base
in E2 a _____________ removes a proton and a halide ion ________ to the proton leaves
strong base rem
halide ion anit
In E2 the _______________ double bond is preferred
more subst double bond
It is easier to control ______________ than E1 vers Sn1
E2 vers Sn2
E2 is not affected by?
steric hindrance
SN2 is affected by ?
steric hindrance
Highly subst carbon chains will undergo
a. E2
b. SN2
a. E2
SN2 vers E2
strong base fav?
E2 vers Sn2
weak lewis base fav?
what things do you modif to fav E2 over E1 and Sn1?
1. pol of solv
2. branch of carbon ch
name react of alkenes
1. polymerization
2. oxid alkenes to form oxiranes
3. ozonolysis of alkens to cleave double bond
4. oxidat of alkenes w KMnO4-
5. hydroboration with diborane B2H6 and peroxide to make an alcohol
6. adding HX to alkenes thr free radic
7. addit of H2O under acidic condit
8. addit of X2 (halogens)
9. addit of HX
10. reduct using metal catalyst
alkenes can be _________ with molec hydrogen and metal catalyst
Catalytic hydrog needs?
hydrog and metal catalyst
reduct of alkenes
typical catalysts are?
platinum, palladium, Raney nickel
Raney nickel is a ?
special powdered form of nickel
Reduct of alkenes is a __________ addit
in reduct of alkenes the 2 hydrog are added to?
same face of double bond
react where one sterioisomer is favored are called?
sterospecific reactions
electroph addit of alkenes
which bond is weaker?
pi bond
Electr on pi bond and are attacked by ?
lewis acids
in electr addit of alkenes lewis acids attack?
pi bond
lewis acids want to accept?
an elect pair
lewis acids are ______________
addit of HX
electr of double bond act as?
lewis base
addit of HX
first step yields a?
2 steps of addit of HX to alkene?
1. double bond reacts w proton
2. halide ion comb w carbocat
in addit of HX
proton adds to form the most?
stable carbocat
addit of HX
proton adds to the ?
less subst carbon atom
Why does the proton add to the less subst carbon atom?
bec alkyl subst stab carbocat
addit of HX
markovnikovs rule says that
proton will add to least substituted carbon,
X will then add to more subst carbon atom
addition of hx
less substituted atom
Markovnikov's rule says that ?
a halide, oh-, etc will add to most subst c in double bond
addition of X2
is a ______________ process
what chemical react is used to test for presence of double bonds?
addition of X2
in addition of X2, the double bond acts as a?
nucleophile and attacks an X2
in addition of X2, the intermediate carbocation forms a ?
cyclic halonium ion.
addition of X2 is syn or anti?
anit. X- attacks cyclic halonium ion in Sn2 fashion
addit of X2 in nucleophilic solvent what can happen?
solv molec can comp in displ step. prod halo alcohol (and not a dihalo compound)
addition of X2 in what can make a halo alcohol?
nucleophilic solvent
addition of H2O.
water can be added to alkenes under?
acidic conditions
addition of H2O follows what rule?
markovnikov rule
addition of H2O
OH will add to ?
more subst c of double bond
addition of H2O is performed at
a. low temp
b. high temp
a. low temp
why is addit of h2O perf at low temperat?
bec otherwise the reverse react will happen.
(acid catalyzed dehydration)
what is the reverse react of addition of H2O to alkene
acid catalyzed dehydration
addition of H2O is carried out indirectly because?
bec yield varies w concentration
How is addit of H2O carried out indirectly?
using mercuric acetate
what is Hg(Ch3COO)2
mercuric acetate
Free radical addition of HX occurs when?
peroxides, oxygen, or oth impurities are pres
Free radical addit of Hx __________ THE MARKOVNIKOV rule
do not follow
Why dont free rad addit of HX follow the markov rule?
bec the X* (radical) adds first to the double bond. making the most stable free radical
free radical addit to alkenes
is useful for which halides?
HBR, but not HCL, or HI
Hydroboroation involves use of ?
diborane (B2H6)
Hydroboration. Diborane.
the boron atom is a ?
lewis acid
hydroboration occurs accord to ?
antimarkov, syn orientation
what are the 2 steps of hydroboration?
1. addit of boron atom to less ster hind carbon
2. oxidat-hydrolysis w peroxide and aq base
what reagents are needed in hydroboration?
H2O2, OH-
oxidation of alkenes
is done with?
oxidat of alkenes with KMnO4 in cold, dilute produces?
1,2 diols (vicinal diols)
1,2 diols are also called?
vicinal diols, glycols
oxidat of alkenes with potassium permanganate (cold, dilute) makes?
1,2 diols (vicinal diols) with syn orientation
hot basic solut of potassium permanganate, then acidified, what happens to alkenes?
1. non term alkenees are cleaved to make a 2 molar equiv of carboxylic acids
2. terminal alkenes are cleaved to form carboxylic acid and carbon dioxide
3. nonterm bond that is disubstituted will yield ketone
With reagants
1.KMnO4, OH-, heat
2. H+
what happens to alkenes
1. carboxylic acids are prod
2. term double bond prod carbox acid and CO2
3. nonterm double bond w disubst carbon will make ketone
ozonolysis of alkenes uses what reagents?
1. O3, CH2Cl2
2. Zn/H2O
ozonolysis of alkenes with ozone and then reduced with zinc and water will prod?
the double bond will split and yield aldehydes
what will this do to an alkene?
1. O3, CH2Cl2
2. NaBH4, CH3OH
split the double bond and make alcohols
alkens pxid with ___________ yield oxiranes (epoxides)
peroxyacetic acid
alkens and CH3CO3H or mcpba will yield?
oxiranes are also called?
mcpba is ?
m-chloroperoxybenzoic acid
how do you make an oxirane?
alkene plus CH3CO3H or mcpba
polymers are?
long chains called polymers of repeating subunits.
the repeating subunits of polymers are called?
polymerization occurs thr what mechanism?
give a typical example of polymerization?
formation of polyethylene from ethylene (ethene)
req high temp and press
CH2=CH2 with R*, heat, high press will make?
a polymer
ethyne is called?
suffix _________ is used for triple bonds
alkynes have ______________ and can be slightly polar
dipole moments. but still pretty small
terminal alkynes are ?
triple bonds can be made by?
1. eliminat of 2 HX from geminal or vicinal dihalide
2. addit of exist triple bond to a nucleophile
eliminat of 2 HX req?
high temp and str base
how do conv a term triple bond to a nucleophile?
by remov acidic prot w a str base to prod an acetylide ion
acetylide ion is used to?
add an exist triple bond to carbon skeleton
partial hydrogenation of triple bonds occurs in what 2 ways?
1. lindlars catalyst to make cis isomer
2. sodium in liquid ammonia bel -33 to prod trans isomer of alkene
reduct of alkynes
LIndlars catalyst is?
palladium on barium sulfate
BaSO4 with quinoline
reduct of alkynes
lindlars catalyst
what does quinoline do?
its a poison that stops the react at the alkene stage
reduct with lindlars catalyst prod?
alkene with cis isomer
reduct with sodium in liq ammonia bel -33 yields?
trans isomer of alkene
reduct with sodium and ammonia occurs thr what mech?
free radical mechanism
electroph addit to alkynes occurs in a ___________ manner?
electroph addit to alkynes can be stopped at _______________________ or carried further
intermediate alkene
free radi cal addit to alkynes add with ___________________ orientation
anti- markovnikov
free radical addit to alkyne
intermediate vinyl radical can?
isomerize to its more stable form
alkynes can be ________________ with B2h6
hydroboration of alkynes is?
syn, boron atom adds first
hydroboration of triple bonds
the boron atom can be replaced with a proton from?
acetic acid
hydroboration of alkyne.
boron atom can be repl with a proton from acetic acid to make a ?
cis alkene
what do you do with terminal alkynes?
use a disubstituted borane to prev further boration of vinylic intermediate to an alkane
hydroboration of alkynes
term alkyne-use disubst borane. VInylic borane interm can be?
oxidately cleaved with hydrogen peroxide
H2O2 is?
hydrogen peroxide
hydroboration of term alkyne
the interm vinyl alcohol rearranges to make?
more stable carbonyl compound
hydroboration of term alkyne
intermediate vinyl alcohol rearranges to more stable carbonyl compound via?
keto-enol tautomerism
alkyes can be oxidatively cleaved with?
1. basic KMnO4, acidification
2. ozone
oxidat of alkynes will yield?
carboxylic acids

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