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EXP-10
CHEM 233L
SYNTHESIS OF p-BROMOANILINE Introduction:
In this experiment, p-bromoaniline was synthesie! in three steps startin" #rom aniline$ %in&e the amino "ro'p o# aniline is a stron" a&ti(ator o# aromati& rin", !ire&t bromination is impra&ti&al )e*'ation 1+$ In or!er to mae a !esire! pro!'&t, amino "ro'p nee!e! to be prote&te! as the a&etami!e whi&h also maintaine! ortho an! para position b't slowe! !own the rate o# rea&tion )e*'ation 2+$ %low rea&tion rate wo'l! in&rease the possibility o# obtainin" the para-position pro!'&t )e*'ation 3+$ he a&etami!e &an be hy!rolye! ba& to the amine )e*'ation .+$ his strate"y o# prote&tion an! !eprote&tion is a (ery important tool in or"ani& &hemistry, espe&ially in m'lti-step synthesis$ Equation 1: NH2
NH2 Br
Br
Br 2
Br
Aniline
plus mono-and-di-derivative mono-and-di-derivative
Equation 2: O
NH2
O
O
O Acetic anhydride anhydride
HN
Aniline
Acetanilide
E*'ation 3/ O
HN
O
Br 2
HN
Acetanilide Br
Bromoacetanilide
Equation 4: O NH2
HN Acid hydrolysis hydrolysis
Br Bromoacetanilide
Br 4-bromoaniline
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Table of Physical data: Compound
NH2
#niline (Cl concentration ater Cl-
Molecular eigh !g"
#mount
$ensity !g%ml"
Moles
0$021
Melting point m&p& oC -$2
'oiling point b&p oC 1.
3$12
2$0 ml
1$021
3$.0
2$0 ml
0$0
0$0.
-11.$2.
-$0
1$01 12$
0 ml
0$0 1$221
---
0 1
100 2.
102$0
2$ ml
1$0
0$0240
-43$1
13
2$03.
3$31.4 "
1$.
0$0.0.
13$1
0$41 "
1$21
0$0014
11.$3
NH3+
#nilinium chloride O
O O
#cetic anhydride O Na+ O-
)odium acetate O
30.
HN
Acetanilide
#cetanilide
)afety notes / • • •
5romine is (ery &orrosi(e$ 6ear "lo(es when 'sin" it$ p-5romoaniline is harm#'l i# inhale! or absorbe! thro'"h the sin 7niline is hi"hly toxi&$ It is possible m'ta"en, sensitier, an! rea!ily absorbe! thro'"h the sin$
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Procedure: EXP-10A: 1$ 8il'te 2$0 ml o# &on&entration HCl in 0 ml o# water in a 12 ml #las, then a!! 2$0" )2$0 ml+ o# aniline$ 2$ %tir the mixt're 'ntil the aniline &ompletely !issol(es$ HCl an! aniline rea&ts #ormin" anilin'm &hlori!e$ )7 rea&tion #or this step was in&l'!e! in yo'r report+$ 3$ 7!! 2$44" )2$ ml+ o# a&eti& anhy!ri!e, stir 'ntil it is !issol(es an! imme!iately po'r a sol'tion o# 3$3" o# so!i'm a&etate in 10 ml o# water into the #las$ .$ 7#ter &omplete a!!ition, stir (i"oro'sly #or min'tes, then &ool in i&e$ Crystalliation sho'l! o&&'r$ 6hen no more &rystals seem to #orm )910 min'tes+, (a&''m #ilter the a&etanili!e, wash the &rystals with small (ol'mes o# &ol! water an! air !ry #or min'tes$ $ P're a&etanili!e is 's'ally obtaine! as white #laes$ :e&rystallie the obtaine! a&etanili!e #rom a minim'm o# hot water$ ;se 10 ml o# water to start an! in&rease the amo'nt o# water !epen!in" on the amo'nt o# a&etanili!e$ $ I# the initial &rystals were not white, a!! 0$" o# !e&oloriin" &har&oal to the pro!'&t in water an! then heat to "ently boilin"$ 4$ :emo(e the &har&oal by hot "ra(ity #iltration ,'sin" two pie&es o# #l'te! #ilter paper$ o a(oi! &ontaminatin" the #iltrate with &har&oal, ! o not o(er#low the #ilter #'nnel$ $ 7#ter re&rystalliation, wash the &rystals a"ain with small (ol'mes o# &ol! water$ $ 8ry the pro!'&t, obtain an I: an! meltin" point$ 10$ he typi&al yiel! is 2$0 "$ %'bmit 100m" o# yo'r pro!'&t an! the rest #or the next experiment$ EXP-10B: #mount $ensity !g%ml"
Moles
13$1
----
1$21
1$0 0$02
1$ ml 2$0 ml
3$11 1$0.
Table of physical data Compound Molecular eigh !g" O
----
Melting point m&p&oC 11.$3
'oiling point b&p&oC 30.
0$023 0$03.
-4$2 1$
$4 114$
HN
Acetanilide
'romine Acetic acid
Solvent
Page 4 O
21.$01
1-1
HN
Br
p-5racetanilide O
21.$01
HN
Br
m-5racetanilide O
21.$01
HN Br
o-5racetanilide +a(),*
10.$0
Reducing agent
Ethanol
.$0
:e!'&e! bromine 2$0 ml
1$.
---
0$4
0$03.2
-11.$1
4$3
Recystallized solvent
Procedure: EXP-10B:
1$ 2$ 3$ .$ $
$
4$
Pla&e 1$0 " o# a&etanili!e in a 0 ml Erlenmeyer #las$ 7!! .$0 ml o# a&eti& a&i! an! swirl 'ntil the soli! !issol(es$ Pla&e a ma"neti& stirrin" bar in the #las an! pla&e the #las on a hot plate an! &lamp$ In the hoo!, obtain 2$ ml o# 1/. o# .$1 M bromine< a&eti& a&i!$ In the hoo!, a!! the bromine !rop-wise 'sin" a !isposable Paste'r pipet o(er a perio! o# min'tes$ he #las was &o(ere! with a small beaer an! stir the rea&tion mixt're #or another 1 min'tes to &omplete the rea&tion$ In the mean time, &lean the 'se! pipet an! "ra!'ate! &ylin!er with 2 ml o# a*'eo's =aH%>3$ 5romine will be !estroye! or its &olor will &han"e #rom re! to &lear by so!i'm bis'l#i!e$ In the hoo!, po'r the rea&tion mixt're into a 10 ml beaer &ontainin" 30 ml o# water$ :inse the rea&tion #las with a!!itional 10 ml o# water$ 7 pre&ipitate sho'l! #orm$
Page -
$
%tir the pre&ipitate with a "lass ro! to brea 'p any &h'ns$ I# the sol'tion still has an oran"e &olor #rom ex&ess bromine, a!! a*$ =aH%>3)so!i'm bis'l#ite+ !rop wise 'ntil the &olor is !is&har"e!$ $ Colle&t the &r'!e pro!'&t by (a&''m #iltration an! wash the soli! . times with 10 ml o# &ol! water )mix e*'al parts o# i&e an! water+$ 10$ rans#er the &r'!e soli! into a 12 ml Erlenmeyer #las$ 11$ :e&rystallie the ma?or pro!'&t #rom a minim'm amo'nt o# hot ethanol$ It is re&ommen!e! to try to !issol(e the soli! in approximately ml o# boilin" ethanol$ 7!!itional ethanol was a!!e! i# ne&essary$ @eep tra& o# the amo'nt o# sol(ent 'se!$ 12$ 6hile heatin", a!! 1ml o# water #or e(ery 2ml o# ethanol 'se! )or hal# the (ol'me+$ 13$ 7llow the sol'tion to &ool !own at room temperat're$ Crystals sho'l! appear$ Chill the &rystallie! material #or min'tes an! then isolate by (a&''m #iltration$ :inse yo'r pro!'&t with &ol! water$ 1.$ 8ry the &rystals o(erni"ht$ 1$ Cal&'late the A yiel!$ >btain an I: an! a meltin" point$ %a(e 100 m" an! s'bmit with other pro!'&t$ he rest is 'se! #or the next step$ Table of physical data: EXP-10C: Compound O
Moles
m&p& oC
0$2
$ensity !g%ml" ---
0$0030
1-1
$043
ml
1$.
0$03
3
20
3$4 142$02.
2 ml 0$342 "
2$13 1$
1$33 0$00220
31 $.
130 ---
.$32
30 ml
2$1
-$4
3$
$..3 .$0
20 ml ---
0$4 0$4
01 -11.$1
1.13 4$3
M !g"
#mount
21.$01
b&p& oC
HN
Br
p.'r.acetanilide O HO
S
OH
O
Conc (2),4 / M +a,( NH2
Br
p.bromoaniline H H
Cl
CH2Cl2 +aCl Ethanol
-----
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Procedure: EXP-10C:
1$
rans#er 1$0" o# p-bromo-a&etanili!e into a 100 ml ro'n!-bottome! #las$ 7!! 10 ml o# water into the #las$ 2$ Chill the mixt're an! a!! 10 ml o# &on&entrate! s'l#'ri& a&i! &are#'lly an! slowly$ 3$ Heat the mixt're to re#l'x #or 1 ho'r$ .$ Initially the p-bromoa&etanili!e will be insol'ble b't as the rea&tion pro"resses it will &ompletely !issol(e$ $ %top the rea&tion an! wait -10 min'tes #or the mixt're to &ool o##$ $ 7nalye the &r'!e rea&tion mixt're by LC by 'sin" 10 ml o# Hex7& )ethyl a&etate+ $ %pot the p-bromoa&tanili!e, the &r'!e mixt're an! a &o-spot an! (is'alie by ;$B$ Estimate the extent o# the rea&tion$ he pro!'&t sho'l! stay at the ori"in$ $ Is there any startin" material le#t Is the rea&tion &omplete I# the rea&tion is not &omplete, &ontin'e the re#'x #or another 30 min'tes to an ho'r$ 10$ ;pon &ompletion, &ool the rea&tion #las an! po'r the &ontents into 20 mL o# i&e!-&ol! water$ 11$ =e'tralie the a&i!i& sol'tion with 10 M =a>H$ heoreti&ally, it sho'l! re*'ire 1 ml o# 10 M =a>H to ne'tralie the s'l#'ri& a&i! present$ 12$ 7!! the a* =a>H sol'tion portion-wise with the help o# a Paste'r pipette$ 13$ 6hen hal# o# the theoreti&al (ol'me has been a!!e! to &he& the pH$ 7!! eno'"h =a>H to brin" the pH to $ I# a !i##erent &on&entration o# =a>H is 'se!, the re*'ire! theoreti&al (ol'me is &al&'late!$ 1.$ rans#er the ne'tralie! sol'tion to a separatory #'nnel an! extra&t the #ree amine with 3 X 10 ml o# CH 2Cl2$ 1$ 5a& extra&t the &ombine! or"ani& layer with 20 ml o# water an! 20 ml o# sat'rate! so!i'm &hlori!e )=aCl+$ 1$ 8ry the CH2Cl2 o(er anhy!ri!e =a2%>.$ :emo(e the !ryin" a"ent by "ra(ity #iltration an! e(aporate the CH2Cl2 in the hoo! o(er low heat$ 14$ :emo(e the sol(ent, as the oily resi!'e be"ins to &rystallie$ 1$ 7llow the &rystals to !ry o(erni"ht$ Che& the p'rity o# the pro!'&t by I:$ 1$ Che& the meltin" point o# #inal pro!'&t an! &al&'late the A yiel!$ :e#eren&e/
