Jawaban PR Ka

7/27/2019 Jawaban PR Ka

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NMR Practice Problems

1) Tell precisely how you would use the proton NMR spectra to distinguish between the following pair

compounds: Bya. I-bromopropaneand2-br?m~propane E(~ ~/v.)jl\ shDtv' OVt(j "2. Fe~kb. prop anal and propanone ~V1a ~('H JL~,.... . ...':-...(~fer te+ (IH~J. cLnt b l-e:f (

c--- .!j-,o~ tc>. ~v.. ::.\"\1). t:.--'\. @ '2 t: .. (1('"'1D. r c. ethyl acetate (MeC02Et) and methyl propanoate (EtC02Me) ., PF

~ d. I-butyne and 2-butyne~ SiVI..c1e-+(b\\"')3lo~@~~~ifr(l J- /'"~ 11--=---.. tt~c.--=-c.J\6.0 I.ZPf"" i'\.eCO'2-e+ -.~ ~auk-f- ~ 'V3ISp~'rr"2) ~ach of the following compounds exhibits a single IH NMR peak. Approximately where would you

each compound to absorb? t-\

a. cyciohexaneo

tV I, I f' P fY\ ~

b. acetone tt3C.;~H3>( tl.') /V r 2~~F-rY' G? -v IffMc. benzene ~ H ti-torpvV'd. glyoxal (ethandial) l-\lri @e. dichloromethane ctt2dz @'"Sff ('(".f. trimethylamine ((CH3)3N)fj c,- I/J /'vM3> /'v ~Ff'~'

~ Lrt33) Draw structures for compounds that meet these descriptions:

a. C2H60; one singlet ~c..-O-c..tt3 /cH3~)

b. C3H7Cl; one doublet and one septet e-\-c--t:!.(~t1 'bc. C4H8Cl20; two triplets c,

'0 0 ~Gf If) Ci.-

d. C4H802; one singlet, one triplet, and one quartet S/\o~ 1;-

4) The two spectra below are of phenol and benzaldehyde. Assign them.

-kr

P

lfl\",Af

100

L-J

5.43

L........J,..,...,....,

515 100

L-.-I I....-...Jj ~


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For each spectrum below, chose between the alternative compounds. Give your reasons.

c.. 0 0

~or ~OH

b I b OHCLi

Courbo'#.~ t\c-

0.86 II IIIGt~J

I

I, , I I

12.5 12.0 11.5 11

J".... "''-207 3 00

I I I

~ I..............I I I

,I I

,I I I

5.0 '.5 '.0 3.5 30 25 2.0 1.5 1.0 0.5 0.0

kr .b

C(H vOH~Ih- orJ..

~h,

tA\c.ohc \

I ii, I I I I I I I I I I Iii8.0 7.5 7.0 6.5 6.0 5,5 5,0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0

b ',C ./'-... ~ ./

./ "V", "-./" 0 r

ot'


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C-~ d c.1 ",/ ~ e-el ;y-{ C. 0;;e.b ~

A,,2-d~~\efVe-~~ q \ ZZ-&.~~'f.j r~

B l,\,2-*v-,& ero~\\e 'f'OfOM-t. .., x The spectra below are of acetone, 1,2-dichloroethane, 1,1,2-trichloroethane, 2,2-dimethoxypropane,

bromopropane and 2-bromopropane. Assign them.

GIl

"'~C!)


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~\ u ~~\ ~'0 U _=-tC ~ bjjV I~ 1\ - I'OM .....I 0. ~ C

~ ~' C ~ A ISAssign the following spectra to one of the compounds listed: 1,4-dimethylbenzene, 1,4-dimethoxybenze

phenylethyne, 3-methyl-3-hydroxy-l-butyne, 2-bromobutane, 1,2-dibromo-2-methylpropane.

C. D ' E F

c. b

,,11'1,,111""1""111,11,11,11"'1,,"111"1,,111111'1,11'1,,111""1,1"1,1111,11'1,1111""1"' jll"I'''II,'I'I'IIII''''I"IIIII''I''''II,,'I''~o ~5 ~o ~5 ~o ~5 4~ 15 10 25 2~ 1~ 1.0 ~5 ~O

b

"""""'!""I""j""!""I"""""""ji"'I"""""""""""""",!,"""""""""i'iii""'j""j""j""j""I""j""j" 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5.:}.0 2.5 2.0 1.5 1.0 0.5 0.0

f

ii j " 'I i " Ij " i 'I " I Ij Iii i i i i Ij i Ii iii Ii i Ii i i " i ij j " , I' " I I I , II I' j " I Ii I 'I ii, II ' j ~ I I' " I Ii I I i I " I i I " , iii " I I I II , I' i " Ii, .. i " j i " iii i iii" iii. 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 .~3.0 2.5 2.0 1.5 1.0 0.5 0.0


5/9

1.00 6.00 3.00W '===! bd

2.012.00bdbd

3.00Id

T

50I I

7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5

Cg H4' 5(" ~T\lJ = I~-~O


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10) Two spectra are given below along with their moleclJlar formulas.

each spectrum. :r.t\b::: g -;.Jl";" 0 (s.a..fu..q-oJ-ed) .

C3H7Cl lA Y\~d'M\Mt2.J~CQ\, 3 ca.N~c;., 3 'i>\


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12) The compound whose proton NMR spectrum is shown below has the molecular formula C3H6Br2. Pro

a plausible structure. c~rt,,&('2. .:I:rtb ~ a--R(7.- 'f:.. 0 ~~.J, ~~~( (3 cSl~~~(~

~,- tL

4.00W

2.01bd

i4~Oi I i ii i , i3~5i iii i I , '3~O' , I ii, I '2~5' , , , I I , , '2~O' , i1~5' iii Iii '1~O' I , , i I I , jO~5' , , I I 'O~O' i

13)A compound (CIOH1202), whose spectJiUmappears below was isolated from a reaction mixture contain

2-phenylethnaol and acetic acid. Propose a structure for this comppund. brh W ~ r~C Ll 0 :rtl h = 2."- ::-12..p. ~C~ V)""'-i +' bull/~ ~d. C ~I.


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) A small plant was adding bromine across the double bond of 2-butene to make 2,3-dibromobutane. A

controller malfunction and allowed the reaction temperature to rise beyond safe limits. A careful

distallation of the product showed that several impurities had formed, including the one whose NMR is

shown below. Determine the structure.

t\

~1.00 2.01

bd bdI; i I "I"

4.5 4.0 3.5

b~.

____ ~J~~ -. '--2.00 3.00

bd bd

d

/

i ( , 3~O... j i , , '2~5' j , , i2~O i , ] i ii '1~5 . i ii i ii '1 ~ci I I I I Iii 'o~5I I i I I f i 'O~Oi

) When 2-chloro-2-methylbutane is treated with a variety of strong bases, the products always seem contai

two isomers (A and B) of formula C5HIO:When sodium hydroxide is used as the base isomer B

predominates. Determine the structures of A and B and explain the experimental results. >Col t>q s.-e

~

..,...t13 c .

tt?>

~

A.

b

c.

V -rE>

-re(~t w)S'MCl.tle.v bq~e


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) A new chemist moved into an industrial lab where work was being done on oxygenated gasoline additive

Among the additives that had been tested she found an old bottle containing a clear, pleasant smelling liq

but missing its label. She took a quick NMR and was able to determine the identity of the compound

without additional information. Can you? The proton NMR is shown below.

) An allylic halide A of formula C5H9Cl undergoes Snl reaction with water to yield a mixture of two

isomeric products, Band C. The proton. ~:~1R spectra ofB and Care Sh0(t). . Suggest structures for A, B

and C. llW .'.. ~./">\\C\ C ,., .~ ~H ~. ~ -':~ \$L-,

B) t\~ ~ ~4 ~ .~~ ~~\" t tfz, OH1 ~~ ~ ~P~l~ , ~~

'2.ti 11-1 tho \ \Y - '\

t

,\~ift/ott,.

trtJ 1

b

d

c~IO.",~1

i4~O' iii ii, '3~5i iii I I I , i3~Oi iii '2~5' Ii' '2~O' ii" '1~5 i I i '1~O' iii , 'O~5' , , 'o~o' i

114

0.52

bd0.56 3.00

W bd "1' '.;"1 1' 1 '.11','1","',"1".11',,'j"",II".I"'IIII"I"'I""'I""II"II"'I""'1 1".,1.' .111,"1.'

6.0 5.5 5.0 4.5 4.0 3.5 . ., 3,0:' 2.5 2.0 1.5 1.0 0.5 0.0

C)

I

e

3.00

bd"'1"11111"1,1111,1111"",.1"1""""'1""""'1""1""1""1.1"1' .. ,11"'1",,,,1"1,,111,1"1,.1'1'1,11"'ljll" I,1

~o ~5 ~o 4~ 4~ 15 10 ~5 ~o 1~ 1~ ~5 ~o

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