Prep 101 Booklet (2013) Part 6
@Prep101
Chem212 Exam Booklet
('10) Ozonolysis
.J
-'-ç,-*\ç.,'
À.-
;Q Ozone adds to the
âlkene
to form an initial ozonide.
The initial ozonide rragments.
-.^--9., U- -
r-C',9.'C'z \ ./ l\ .C'.-../ r /\ ,ô-ooj ' '9-9' Oaonide
The lragmenls recombine to form the ozonide.
Àldehydes
Oimethyl
andoa lêtones
sulloxide
î.ô06
700? .'-
(r/6/(?, l{,21,74 Qé ,2J,s2 ,s5
'1
?ætu
Dtc
a, I ), l3, eQ ,27,7 ?"^ttr *ï s"
[ ,i
ÿ".ttV #3
2oo?- 4ttr< 8
k,
,,^
e^,tY
[û"L
t. Ot
-^
It^È
2. DNî
fu
vocb
sn
\*t*
) lôé tl0" ) toe ,ll[, I 2 ' ) (gh â*,\ /,/ i 2,,, c,)
;\î'4* ,o^oot
/,Lk *b,Dl
"\('vailrt'
*" Z.DMs o
n
)\n'trry"u
Solutions will be posted at www.preplol.com/solutions
112
@Preplo1
5.4 1.
Chem212 Exam Booklet
Practice Problems Which of the following would not undergo rearrangement?
Àt cHlat{êHcHl -+ I Clilt /-CY.3 ,1, t eEtcttacHl .t ct3
Dt
üi:i |
CH3Ci:iirl'
El ('H r
cri3\ I \
CcHCI;'iiJ:
t-t1 "
cl3
cE3 I
CE3C@lcBj
2.
Which has lowest heat of hydrogenation?
E) CH1 X \/ C-C /\l c< ll /\ tr
arzàolz(,r2c*d2 !) CE2-(lClla, li
^:
o{
ll
c) *t, o< /\
CAI
lt Cllt
/o'*t
llf,
Dr
ta \/
lt
CS3 C< \/\ OrC /\ t{
J.
Ctl
li
*r1ci proAuct r.ould
)"ou
att,.c! !!ü t!|. rcid-c.r.1y:.d .ddi'gloc of
M' lÀ7"* r
ri>
\,
À{,^,*'y$"' tr ù
vox
Solutions will be posted at www.prep10l.com/solutions
113
OPrep101
4.
Chem212 Exam Booklet
Give the structure(s) of the principle organic products of the following reac{ions. Where appropriate the struclures must andicete the slereochemistry of the compound.
(a)
1. B"H"
2. ff2O"2tOH-
--+
Which of the followinqwould not undergo rearangement?
,/ \it CRJCHCHCT{I c:lt3
B)
al3
D)
+l
cng
cr3
B'
I
'e9 ol3
I
I
cE3CECCE3
CIl3 CCt{Ct{,CHa
&"-
È-J
cli
ct ,/Gà-il
q(3cCE2CEj
6. l0hêc producE Dould laruLÈ
froû tbè tollorttE reècElon? xroridls + H&->?
æooeo eo.q t..
Br
8r I
H00
br
t[
v
Solutions will be posted at www.prep101.com/solutions
114
It @?rep101 r
7.
{ Àÿ"r # $".
Chem2l2 Exam Booklet
qlp.i"o"
Give the detailed reaction melhanism for the chlorohydrin formation of 1-methylcyclohexene, incrudins
"..T r'-'J":ild
stereo
sTâdeta,s
û+-Ur,{ FÔ
8.
- \,J
What product forms if 1-methylcyclohexene is reacted with Br2lccl1? Also address chirality
issues.
Br
I
ra (--,
9.
cl
bE CCI,]
r'6'"'r'
The deuterated alkene below is hydrogenated with hydrogen gas and a platinum catalyst. The reâction proceeds with syn (same side) addition.
H,
H2/Pt
ob The main product is
AphB
C
D
'ôvo
,k7o
D
Ph
Ph
Solutions will be posted at www.prep10l.com/solutions
115
Chem212 Exam Booklet
@Prep101
10.
The diene below is reacted with excess of hydrogen iodide. The most likely products are
rY
(structural isomers only being considered, not stereoisomers)
\__-/
^,-^----------, \,
'={-V \-/\,
\__/
B
D a mixturc of B and C
11.
Draw structures for the most appropriate reaclant (A). Clearly indicate stereochemislry where necessary.
Hg(OAc)2, H2O
A
NaBHa
-->
12.
ln each of the following questions, select the conect compound.
(a)
o A1
Cr A2
er'oo* A3
u A1
Reacts fastest in electrophilic additions (e.9. with 812 in CCl4): Reacts slowest in electrophilic additions (e.9. with B12 in CC14):
Solutions will be posted at www.prep10l.com/solutions
116
OPreplO1 13.
Chem2L2 Exam Booklet
2,3-dibromobutane, shown below in Fischer projection, cân only be obtained by addition of Bh to:
CHs
1-butene B) (Z}2-butene
A)
14.
C) (E)-2-butene D) 2-methylpropene
Complete the following reaction schemes:
ü+i BH3 2 H2orroHlH2o l.
Solutions will be posted at
//
_J
l. H8l/H3o'
\
2'NaBH1
www.prep101.com/solutions
117
OPrep101 15.
Chem212 Exam Booklet
A studenl attempted to synthesize ether (lX) from alkene
(V
) using H+/MeOH but ether (X)
was obtained instead. OIUe
-r... / br.
\-\
-l o'ur)
(L\)
.ÿ^!/O\te
-l
(x)
Answer the following questions:
(a) Explain this result by providing a suitable mechanism.
(b) Provide an allernative route for the synthesis of ether (lX) from alkene (Vlll).
(c) Provide a synlhesis of ether (Xl) from atkene (VIl).
Solutions will be posted at
www.prepl0t.com/solutions
1'18
Chem212 Exam Booklet
O Prep101
16.
Shou, the key products from the information provided:
Compound A has formula CsHr.{. When compound A is subjected to hydroboration, cornpounds B and
C are formed in a racemic mix. When compound A is subject to H2O/H+ compound D is formed, which is non-chiral and has the same formula as B & C. When B or C is subiecl to concentrated HrSO1, it is determined that A is reformed, but when D is subjected to concentrated H2SO. A and E are formed. Catalytic hydrogenation
d
A yields ethyl cyclohexane.
(^--€\ÇH.r
i
ll. .-.\rZ
,Æl
r
17
.
1
IA
lll'il
llyd,.i,-rr,*
----+
ll
i
1. Complete the following reaction:
"'>_\{< .or+_yo H}I
"''îi:
')'Y ')A. ' -\/ [L,, -é +ï* 1,
Solutions will be posted at www.prep101.com/solution
s
121
O Prep101
22.
Chem212 Exam Booklet
The observed products in the ozonolysis of 2-methyl- j ,4-pentadiene would be:
u-(." *4,,o, * ,\_, \-_-._ ____z lr i44h.ÿ41
H--< \\
(d)
23.
_o
'tt
Draw the structures of the major products of the following reactions. Show stereochemistry. (a)
, )
"""._
2. Na}!SOs, H2O
\
x':,
(b)
\'
ll....-
Br2,
cct.
§
Solutions will be posted at
www.prepl0l,com/solutions
122
/5 &z,"dl.
?or? --/
-t
Chem212 Exam Booklet
@Prep101
Chapter Six: Alkynes
6.1
Naming Alkynes
Some common names of alkynes:
Ethyne (Acetylene)
il/;(" ,-/,*H-c=c-H
l*gYuu$-c=c-H ^'lLurn, ,lrÿ -lL.-/* -,\-,^:,,-_-,,. 'm#*"*'*"t-'-c-cH3 H3C-CH-C-C-H
Propynê (Methylacetylene)
2-Butyne
.=/Wy
3-butyn-2-ol
OH
H3C-C=C-1H-CH2CH3
OCH3
4-methoxY'2'hexYne
Preparation of Alkynes
.
Treetment of a dihaloalkane with a strong base (NaNHr) results in the twofold elimination of HX end formation of an alkyne.
Br
o^r.Acetylide
.
et'*s
Àe'r.
\
anions
The enhânced acidity of terminal
[Ka
= ZS1 allows them to be deprotonated by
strong bases (usually NaNHr) yielding acetylide anions.
sp oÂ
ën
4 pl(c=25
ô )$a,o"h*
J
NH2 lll
acetylide anion
I
,.[HP-
*
v--Na
I
(. 1"."
r(ç,*
*
ÿ,,1ûpl1^
pKa = 40
#^
/*tu*/
?-r
o*l'*
/-,-
^r*ru, ç,h|. /wo"|'w(sU) lno
Solutions will be posted at www.prepl0l.com/solutions
.--
123
*e@ ,U,/ç â,/^r
@Prep1ol
.
Acetylide anions can be alkylated with gfi{nary (or methyl) alkyl halides making a new C-
bond. -n*roq *!:"1, ->*rou 4*:^t., .-: ?:fuyù'' ï-.._-
,a /-'/
c
=J/z .
Chem212 Exam Booklet
I
,-5Az
HCr
qr
rl'\ W
Hcl -_-+
no
readion
Double bonds react with electrophiles to give addation products, while benzene reacts lo give substitution products
\1
Brz
Br. \/
Br
O.*r ô
CrlrAcyç **î*on
()
Y
-B'
Br not thisl!
h6 ,A*d,( S,ltl = -trd,
Solutions will be posted at
www.prepl0l.com/solutions
134
Chem212 Exam Booklet
OPrep101
7.4.1 Reagents for Electrophilic Aromatic Substitution (EAS)
tlI l"
IL
.lnmanycasestheactiveelectrophileisnotavailableasadiscre4species,thereforeweneed
tryIf.lEfrrê.ètëdt'dpïlflq
to ensure reaction with the aromatic system
Reagents
used to carry
Active electrophilic sPecies
out transformation lodine, bromine and chlorine are too unreactive to act as electrophiles for EAS
Brz + FeBrs
Nitration Noz
tfrSO. *
nHO. +
H2O + HSOI-+ NOz'
H2SOI + ;'1116,
Noz'
Fuming HzSOa
SOr
RCOCT + AtCl3
RCO'(ArCll)-
Sulfonation So:H Friedel-Crafts Acylation RC=O
Friedel-Crafts Alkyation
R=alkyl
R can rearrange
duting reaction
RX + AlCl3
R6*-x-Alch'
ROH + H.
'R.
Olefin + H'
R.
Solutions will be posted at www.prep101.Gom/solutions
135
rtry 5,ôs[,
OPrep10l
Chem212 Exam Booklet
7.4.2 Mechanism of EAS
o
All electrophilic aromatic substitution reaciions involve three $eps:
'1. The formation
of an electrophile (an electron deficient species)
2.
Reaction of the etectrophile with the pi etectrons of the aromatic ring
3.
Proton transfer from the cation intermediate to regenerate the aromâtic character of the ring (net effect of steps 2 and 3 is lhe substitution of an aromâtic H- for the E.)
Overall reaction:
E++
Step
1:
+H*
Formation of the
aw a
l'{ci;
L.
G, 1'(^
(rba/^ El REASON foT EAS:
,\y
4*l
C»..
Ho
\____,
Benzene is "electron rich' with accessible pi
'\Lp/ob^atb"
*
with electrophiles)
Arometicity is regained (substitution and not addition) Resonance stabilzed intermediate
Solutions will be posted at www.preplol.com/solutions
w
ea'dou À-^
^ in
z
ylc"
'136
a)!
.t
OPrep101
Chem212 Exam Booklet
NOTE: Benzene is still a weak nucleophile so need strong electrophiles like X+
*"/
r/,*,
t ,r*rr/r;7ile ù ,,,-o d
co-,ra/a|. t
;t.
dlssosiatês to form â posltiy, Bromln.lon and FaBr..,
ît!
x
* Ba"
ô
Fe-
7.4.3 Specific EAS Reactions (a) Halogenation
Aromatic rings can be chrorinated with chrorine and iron bromination above)
Çlz
(*)
chroride cataryst (anarogous to
ct
(/ -Ec- O N/"-f"»u' Solutions will be posted at
I
ü'n'z,-ff! Bil^, (e.,,*1u,4*
/solutions 6*,a
^*--ilàl
Chem212 Exam Booklet
('10) Ozonolysis
.J
-'-ç,-*\ç.,'
À.-
;Q Ozone adds to the
âlkene
to form an initial ozonide.
The initial ozonide rragments.
-.^--9., U- -
r-C',9.'C'z \ ./ l\ .C'.-../ r /\ ,ô-ooj ' '9-9' Oaonide
The lragmenls recombine to form the ozonide.
Àldehydes
Oimethyl
andoa lêtones
sulloxide
î.ô06
700? .'-
(r/6/(?, l{,21,74 Qé ,2J,s2 ,s5
'1
?ætu
Dtc
a, I ), l3, eQ ,27,7 ?"^ttr *ï s"
[ ,i
ÿ".ttV #3
2oo?- 4ttr< 8
k,
,,^
e^,tY
[û"L
t. Ot
-^
It^È
2. DNî
fu
vocb
sn
\*t*
) lôé tl0" ) toe ,ll[, I 2 ' ) (gh â*,\ /,/ i 2,,, c,)
;\î'4* ,o^oot
/,Lk *b,Dl
"\('vailrt'
*" Z.DMs o
n
)\n'trry"u
Solutions will be posted at www.preplol.com/solutions
112
@Preplo1
5.4 1.
Chem212 Exam Booklet
Practice Problems Which of the following would not undergo rearrangement?
Àt cHlat{êHcHl -+ I Clilt /-CY.3 ,1, t eEtcttacHl .t ct3
Dt
üi:i |
CH3Ci:iirl'
El ('H r
cri3\ I \
CcHCI;'iiJ:
t-t1 "
cl3
cE3 I
CE3C@lcBj
2.
Which has lowest heat of hydrogenation?
E) CH1 X \/ C-C /\l c< ll /\ tr
arzàolz(,r2c*d2 !) CE2-(lClla, li
^:
o{
ll
c) *t, o< /\
CAI
lt Cllt
/o'*t
llf,
Dr
ta \/
lt
CS3 C< \/\ OrC /\ t{
J.
Ctl
li
*r1ci proAuct r.ould
)"ou
att,.c! !!ü t!|. rcid-c.r.1y:.d .ddi'gloc of
M' lÀ7"* r
ri>
\,
À{,^,*'y$"' tr ù
vox
Solutions will be posted at www.prep10l.com/solutions
113
OPrep101
4.
Chem212 Exam Booklet
Give the structure(s) of the principle organic products of the following reac{ions. Where appropriate the struclures must andicete the slereochemistry of the compound.
(a)
1. B"H"
2. ff2O"2tOH-
--+
Which of the followinqwould not undergo rearangement?
,/ \it CRJCHCHCT{I c:lt3
B)
al3
D)
+l
cng
cr3
B'
I
'e9 ol3
I
I
cE3CECCE3
CIl3 CCt{Ct{,CHa
&"-
È-J
cli
ct ,/Gà-il
q(3cCE2CEj
6. l0hêc producE Dould laruLÈ
froû tbè tollorttE reècElon? xroridls + H&->?
æooeo eo.q t..
Br
8r I
H00
br
t[
v
Solutions will be posted at www.prep101.com/solutions
114
It @?rep101 r
7.
{ Àÿ"r # $".
Chem2l2 Exam Booklet
qlp.i"o"
Give the detailed reaction melhanism for the chlorohydrin formation of 1-methylcyclohexene, incrudins
"..T r'-'J":ild
stereo
sTâdeta,s
û+-Ur,{ FÔ
8.
- \,J
What product forms if 1-methylcyclohexene is reacted with Br2lccl1? Also address chirality
issues.
Br
I
ra (--,
9.
cl
bE CCI,]
r'6'"'r'
The deuterated alkene below is hydrogenated with hydrogen gas and a platinum catalyst. The reâction proceeds with syn (same side) addition.
H,
H2/Pt
ob The main product is
AphB
C
D
'ôvo
,k7o
D
Ph
Ph
Solutions will be posted at www.prep10l.com/solutions
115
Chem212 Exam Booklet
@Prep101
10.
The diene below is reacted with excess of hydrogen iodide. The most likely products are
rY
(structural isomers only being considered, not stereoisomers)
\__-/
^,-^----------, \,
'={-V \-/\,
\__/
B
D a mixturc of B and C
11.
Draw structures for the most appropriate reaclant (A). Clearly indicate stereochemislry where necessary.
Hg(OAc)2, H2O
A
NaBHa
-->
12.
ln each of the following questions, select the conect compound.
(a)
o A1
Cr A2
er'oo* A3
u A1
Reacts fastest in electrophilic additions (e.9. with 812 in CCl4): Reacts slowest in electrophilic additions (e.9. with B12 in CC14):
Solutions will be posted at www.prep10l.com/solutions
116
OPreplO1 13.
Chem2L2 Exam Booklet
2,3-dibromobutane, shown below in Fischer projection, cân only be obtained by addition of Bh to:
CHs
1-butene B) (Z}2-butene
A)
14.
C) (E)-2-butene D) 2-methylpropene
Complete the following reaction schemes:
ü+i BH3 2 H2orroHlH2o l.
Solutions will be posted at
//
_J
l. H8l/H3o'
\
2'NaBH1
www.prep101.com/solutions
117
OPrep101 15.
Chem212 Exam Booklet
A studenl attempted to synthesize ether (lX) from alkene
(V
) using H+/MeOH but ether (X)
was obtained instead. OIUe
-r... / br.
\-\
-l o'ur)
(L\)
.ÿ^!/O\te
-l
(x)
Answer the following questions:
(a) Explain this result by providing a suitable mechanism.
(b) Provide an allernative route for the synthesis of ether (lX) from alkene (Vlll).
(c) Provide a synlhesis of ether (Xl) from atkene (VIl).
Solutions will be posted at
www.prepl0t.com/solutions
1'18
Chem212 Exam Booklet
O Prep101
16.
Shou, the key products from the information provided:
Compound A has formula CsHr.{. When compound A is subjected to hydroboration, cornpounds B and
C are formed in a racemic mix. When compound A is subject to H2O/H+ compound D is formed, which is non-chiral and has the same formula as B & C. When B or C is subiecl to concentrated HrSO1, it is determined that A is reformed, but when D is subjected to concentrated H2SO. A and E are formed. Catalytic hydrogenation
d
A yields ethyl cyclohexane.
(^--€\ÇH.r
i
ll. .-.\rZ
,Æl
r
17
.
1
IA
lll'il
llyd,.i,-rr,*
----+
ll
i
1. Complete the following reaction:
"'>_\{< .or+_yo H}I
"''îi:
')'Y ')A. ' -\/ [L,, -é +ï* 1,
Solutions will be posted at www.prep101.com/solution
s
121
O Prep101
22.
Chem212 Exam Booklet
The observed products in the ozonolysis of 2-methyl- j ,4-pentadiene would be:
u-(." *4,,o, * ,\_, \-_-._ ____z lr i44h.ÿ41
H--< \\
(d)
23.
_o
'tt
Draw the structures of the major products of the following reactions. Show stereochemistry. (a)
, )
"""._
2. Na}!SOs, H2O
\
x':,
(b)
\'
ll....-
Br2,
cct.
§
Solutions will be posted at
www.prepl0l,com/solutions
122
/5 &z,"dl.
?or? --/
-t
Chem212 Exam Booklet
@Prep101
Chapter Six: Alkynes
6.1
Naming Alkynes
Some common names of alkynes:
Ethyne (Acetylene)
il/;(" ,-/,*H-c=c-H
l*gYuu$-c=c-H ^'lLurn, ,lrÿ -lL.-/* -,\-,^:,,-_-,,. 'm#*"*'*"t-'-c-cH3 H3C-CH-C-C-H
Propynê (Methylacetylene)
2-Butyne
.=/Wy
3-butyn-2-ol
OH
H3C-C=C-1H-CH2CH3
OCH3
4-methoxY'2'hexYne
Preparation of Alkynes
.
Treetment of a dihaloalkane with a strong base (NaNHr) results in the twofold elimination of HX end formation of an alkyne.
Br
o^r.Acetylide
.
et'*s
Àe'r.
\
anions
The enhânced acidity of terminal
[Ka
= ZS1 allows them to be deprotonated by
strong bases (usually NaNHr) yielding acetylide anions.
sp oÂ
ën
4 pl(c=25
ô )$a,o"h*
J
NH2 lll
acetylide anion
I
,.[HP-
*
v--Na
I
(. 1"."
r(ç,*
*
ÿ,,1ûpl1^
pKa = 40
#^
/*tu*/
?-r
o*l'*
/-,-
^r*ru, ç,h|. /wo"|'w(sU) lno
Solutions will be posted at www.prepl0l.com/solutions
.--
123
*e@ ,U,/ç â,/^r
@Prep1ol
.
Acetylide anions can be alkylated with gfi{nary (or methyl) alkyl halides making a new C-
bond. -n*roq *!:"1, ->*rou 4*:^t., .-: ?:fuyù'' ï-.._-
,a /-'/
c
=J/z .
Chem212 Exam Booklet
I
,-5Az
HCr
qr
rl'\ W
Hcl -_-+
no
readion
Double bonds react with electrophiles to give addation products, while benzene reacts lo give substitution products
\1
Brz
Br. \/
Br
O.*r ô
CrlrAcyç **î*on
()
Y
-B'
Br not thisl!
h6 ,A*d,( S,ltl = -trd,
Solutions will be posted at
www.prepl0l.com/solutions
134
Chem212 Exam Booklet
OPrep101
7.4.1 Reagents for Electrophilic Aromatic Substitution (EAS)
tlI l"
IL
.lnmanycasestheactiveelectrophileisnotavailableasadiscre4species,thereforeweneed
tryIf.lEfrrê.ètëdt'dpïlflq
to ensure reaction with the aromatic system
Reagents
used to carry
Active electrophilic sPecies
out transformation lodine, bromine and chlorine are too unreactive to act as electrophiles for EAS
Brz + FeBrs
Nitration Noz
tfrSO. *
nHO. +
H2O + HSOI-+ NOz'
H2SOI + ;'1116,
Noz'
Fuming HzSOa
SOr
RCOCT + AtCl3
RCO'(ArCll)-
Sulfonation So:H Friedel-Crafts Acylation RC=O
Friedel-Crafts Alkyation
R=alkyl
R can rearrange
duting reaction
RX + AlCl3
R6*-x-Alch'
ROH + H.
'R.
Olefin + H'
R.
Solutions will be posted at www.prep101.Gom/solutions
135
rtry 5,ôs[,
OPrep10l
Chem212 Exam Booklet
7.4.2 Mechanism of EAS
o
All electrophilic aromatic substitution reaciions involve three $eps:
'1. The formation
of an electrophile (an electron deficient species)
2.
Reaction of the etectrophile with the pi etectrons of the aromatic ring
3.
Proton transfer from the cation intermediate to regenerate the aromâtic character of the ring (net effect of steps 2 and 3 is lhe substitution of an aromâtic H- for the E.)
Overall reaction:
E++
Step
1:
+H*
Formation of the
aw a
l'{ci;
L.
G, 1'(^
(rba/^ El REASON foT EAS:
,\y
4*l
C»..
Ho
\____,
Benzene is "electron rich' with accessible pi
'\Lp/ob^atb"
*
with electrophiles)
Arometicity is regained (substitution and not addition) Resonance stabilzed intermediate
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Chem212 Exam Booklet
NOTE: Benzene is still a weak nucleophile so need strong electrophiles like X+
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Aromatic rings can be chrorinated with chrorine and iron bromination above)
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