Chem LLZA, Fall?

:OLZ, NMR Worksheet # 3

Due

at 8:7A am in Lecture on Tuesday, November 73. You moy work in small graups for this

assignmenL

L"ffffirff,il}*utq
hydragcn otomsthatcon

Cpluplets A, B,

what muhipticity orQ-

is expected

for each resonance? lossume thot theR sroupsdo not contain

C: +rrylc.f
i{otatlon Ereraph:
The fslloryirry

spllttingtree predicts the apparance of multlplet B lf

J1g

= 6 Ht and Jgc= 5 Hr:

{a i -:-'-i- -i*-"i--' :iii :,': lrl

''1 -

r,-l*-i -j iiil l--;_.1alii

..

i'-.
l

iB

b. Draw a splitting tree to predict the appearance of

multi&t

lf

lp

= 10 Hz and Js6 = 4 Hr. Drsw the spHtting Jp

flrs, then

b. Zoom in on the multiplet centered near 2.2 ppm. This multiplet can be described as two overlapping triplets. Explain why this
is

not called a "doublet of triplets".

TtU fwo k',ftu{ arX

6e56,tol,l

vl tvtod^'W^l l*h^\;

,tof otr

1.'l*'r

wc'v'1

*flil'

Luk,

the multiplet shape from part b in the space below, and then label it with letters (from the structure of trimyristin)to indicate which triplet is which.

il

,,D'

d. Justify your answer to part c in 10 words or less.

Ll1'dw'r tly Ha tottrl. te

on

lq A'
B

e. The hydrogen atoms labeled D and D' are technically diastereotopic for the same reason that A and B are. However, D and D'

do not appear different from each other in the observed spectrum, while A and for this observation.

do appear different. Propose an explanation

Fro-n /0ro"l TtrVu,hvt, lft an rln*k2^) ,! it tvo C- a-"g h c Ly, d,htkna u FL

( tklu'L*l '"t'l lh*/ tk^r* t r A'4Js),

)\zl*'zts

f.

the peak picking tool to label the exact chemical shift of the multiplets corresponding to hydrogen atoms labeled A and B. Display the peak labels in Hz. (Right click on the spectrum, seled properties, open the peoks tab then change ppm to Hz in the units field). Copy the peak yalues {in Hz} above each of the peaks in the picture below. Next, construct a splitting tree above each multiplet to show why each is considered a doublet of doublets.
Use

.R

ryp XH e( t-{
1l

$.
{J 'tc6
t

14

ut

s
n6
I

\ \ .f. ri .:
-_a,

$o
L'r

.rq\

:rI

.Y

-$ .>
c{
I

:> "td l1

-r>

4.29

4.27

4.25

4.29 4.21 4.19 417 4.15 4.13 4.11 4.09 (ppm)

4.O7

g. ln lecture, the calculated coupling coostants of 4.2 Hz, 6.1 Hz, and 11.9 Hr were stated corresponding to these multiplets. Show a sample calculation {subtract one peak location from another} leading to each of these values.

4.2H2:
6.1

JSbl,lJ-

1557,

\]

Hz:
Hz:

ll
fr

b7,\ 0- Aq bl,78

11'e

I ut "z

l-

U\q,8 0

h. Computer programs can be used to predict the expected multiplet shapes for peaks with given coupling constants. One such progrirm is available on the following website: htto://www.colbv.edu/chemistrv/NMR/first.html Using this proSram and the coupling constants 4.2 and 6.1, the following multiplet shape was predicted for the hydrogen labeled C in the previous diagrams. (Try it yourselfl) Wo* backwards from this prediction to sketch a splltting tree in the space abwe it which shows how the computef calculated this diagram.

Y, 1

T,L/,I

The computer predlaion

for multiplet A

i. ln the actual spectrum of trimyristin, this multlplet has a slightly different appearance (it is not possible to discern 9 distlnct peaks). Zoom in on this region of the spectrum to examine the peak. Then sletch the obsenrcd muhlplet superimposed on the prediction below to show how the prediction corresponds with the observed shape, Then erqlaln your sketch in 10 words or
less.

Explain:

Pe*lcs

o*la1l

^t ,not stt^rjAr h\a

3.

Consider the following six alkyl bromides, which were starting materials in the nucleophilic substitutions lab experiment last

week. a. for each strudure, label the positions wlth letters to indicate which hydrogen atoms are magnetically different from each

other. The first is done for you as an example: b. Use the label "A" for the most deshielded hydrogen.
c. Don't forget to give diastereotopic hydrogen atoms different letters from each other. lf diastereotopic hydrogen atoms are predicted, please draw the hydrogen atoms explicitly. Otherwise, you may use the abbreviation shown below in which the

hydrogen aJoms are implied by the bond{ine notatlon. d. Create a table that lists the integral and the muhiplicity that would be expected for each resonance. lf a complex multiplet is expected, also predict the "apparent" multiplicity (what would be observed if all of the vr'crnol coupling constants were identical and no geminol coupling was observed.)

integral

multidicity

apparent muttiplicity if allJ valuea equal

DB ,/-\. ECA

...8r

A2 B2 c2 D2 E3

triplet

triplet of triplets (apparent quintet) (apparent quinte$ triplet of triplet of quartets (apparent sextet)

fidets

triplet

,"ffs,

(=l P=3 Fsl br3

A' B:

A,Ll )-

ll/a

ttNl I

Jlt

a,pltt*nl ,ex kl, a77a.a* C u."ft, *r X*n*?':t ^l f orVT^r*/ <cpW

/-Au*
t ^hluf

d/.)Lo

y@ <tybf
fnY

afTarthf

b'l'

/4.-I I' Ll (z L

L*
+

aPPaftnl X*'vtc*

h"L b,
I

rrt-'

,lt

'{f**

'n"net

L'
rHc

/o

iL

tVu'
HA

integral
Hg

multiplicity 5

apparent multiflicity if all J values equal

th

!y"
Hp

zA3

/1re e=?

5.

Br

Br'

d
A')
9rl
Crl
Drl
F--l

dd - "Ff.tt,ltvl lll/ ' ,fp fw+,kt B,'7 Lr& AliA - elq gr,uutz-l Q= )" adA - W: g-utl+f f ; L ddl ' g u'"ful
h'I

rf

IJ
d

F"l

//t / / lili Jl) t/tdl

ttl

h.l

dil

^Pf

"lp, kyl+f
L**n'

/,T[; :i/ AlP UIH:

elP / n".4

ayp. *oYltl

Hl,

ArL
tlr- B=3

/
tt
apfa<r'&r*7***1

iW:,
4.
sections.

:::

ii]

arvarea*t'*vte+

The folder of NMR files contains aEtual NMR spectra of samples taken from the dropper bottles in one of last week's lab

a. Open each spectrum one at a time (using the processing template provided in the same folder). For each speqtrum, carry out

the same steps that were listed in the MNova tutorial earlier this week. {lllnt: read questlon 5 before you spend too much tlme figuring out whlch spectrum belongs to whlch compoundl
b. Attach the resulting printouts, in alphabetical order (T, U, V, W, x, Y, Z), to this worksheet. c. Place the letters T-Z in the box to the left of each of the structures in question 3 to indicate which structure corresponds to

which spectrum.

d. Use the labels from question 3 when you annotate these spectra, and don't forget to edit the integral for each "A" peak to match the number of "A" hydrogen atoms ln your prediction.

5.

One of the useful features of NMR is that the integral values allow accurate determination of the ratios of compounds in a

mixture. Therefore, NMR can be used to determine if a sample is pure or not, and if not, to determine the relative amount
of the impurity. Two of these NMR spectra reveal that the material is not completely pure. One of them cofltains

approximately 59( of a second compound as an impurity, and the other contains approximately 2596 of a second compound as an impurity (4r1 ratio desired:undesired compound). Which wo spectra are these?

i. ii.

S%impurity:
Z5i%lmpurity;

Y Z

c. Draw a splitting tree to predict the appearance of multiplet B if 16 = 10 Hz and

JEc

= 4 Hz. This time, draw each splitting

llt

flrst, then the splitting

J4s:

d6a=\H-

= YHz

i*tl

.foH;

d. Compare the final predictions from parts b and c. Do they match? Why orwhy not?

ratdy

Eo*L 1,otta5 a/a t|l,th\ &.tc l,*fly {,rts gn srl*hJ

H, ** th

<an.

**cr'

sytttttS *ur9

c,*e.\ y@feag @,r!-a'b*,!w.

e. Draw a splitting tree to predict the appearance of multlplet B if J6 = 8 Hz and Jrc = 6 Hz:

&e= {tt*_
f,0. =,bllt-.
'

[gc= 6-liz-

2.

Open the Trimyristin

lH

NMR spectrum in MNova.

03)

b0z
d

3->

a. On the structure above, label each of the positions on the alkyl chains witli the observed chemical shift from the spectrum. lnclude chemical shifts for the hydrogens which have not been labeled with letters.

'i'25 '{'t6(e(il 6)

2.37 2.36 2.11 2.10 2.09 2.09 1.74 HDO 1.73 HDO 1.72

Alkyl-Bromide-T.1.1.1r Alkyl-Halide-J

4.5E+08

4.0E+08

C,D
3.5E+08

3.0E+08

2.5E+08

2.0E+08

1.5E+08

B
1.0E+08

5.0E+07

0.0E+00
6.00 3.01 6.01

8.0

7.5

7.0

6.5

6.0

5.5

5.0

4.5

4.0

3.5 f1 (ppm)

3.0

2.5

2.0

1.5

1.0

0.5

0.0

-0.5

Alkyl-Bromide-U.1.fid Alkyl-Halide-G

3.27

1.05 1.05 1.04 1.04

750 700 650

600 550 500 450 400 350 300 250 200 150 100 50 0

2.03

9.00

-50 0.5 0.0 -0.5

8.0

7.5

7.0

6.5

6.0

5.5

5.0

4.5

4.0 3.5 f1 (ppm)

3.0

2.5

2.0

1.5

1.0

1.91 1.90 1.89 1.88 1.87 1.86 1.85 1.84 1.84 HDO 1.82 1.81 1.79 1.06 1.04 1.02 1.02

3.97 3.96 3.95 3.95 3.94 3.93 3.93 3.92 3.91

Alkyl-Bromide-V.1.fid Alkyl halide D

750 700 650

600 550 500 450 400 350 300 250

B
200 150

100 50 0

1.00

4.12

6.16

-50 0.5 0.0 -0.5

7.5

7.0

6.5

6.0

5.5

5.0

4.5

4.0

3.5 f1 (ppm)

3.0

2.5

2.0

1.5

1.0

Alkyl-Bromide-W.1.fid Alkyl halide E

3.31 3.31 3.30 3.30 2.01 2.01 1.99 1.99 1.99 1.98 1.98 1.97 1.96 1.96 1.94 1.94 1.62 1.62

1.04 1.04 1.03 1.02 1.02 1.02

600

550

500

450

400

350

300

H2O A

250

200

150

100

B
50

0
2.00 1.00 1.09 6.01

-50 0.5 0.0 -0.5

7.5

7.0

6.5

6.0

5.5

5.0

4.5

4.0 3.5 f1 (ppm)

3.0

2.5

2.0

1.5

1.0

Alkyl-Bromide-X.1.fid Alkyl-Halide-I

7.5 7.0 6.5 6.0 5.5 5.0 4.5

4.0 3.5 f1 (ppm) 3.0 2.5

2.00

2.0
4.06 1.05

C,D

1.5 1.0 0.5 0.0 -0.5

3.07

F,G

4.24 4.23 4.23 4.22 4.21 4.20 4.19 4.18 2.20 2.19 2.18 2.18 2.17 2.16 2.15 2.14 2.13 1.89 1.88 1.86 1.85 1.84 1.84 1.83 1.82 1.80 1.79 1.79 1.78 1.76 1.74 1.63 1.62 1.61 1.60 1.58 1.58 1.57 1.56 1.55 1.45 1.44 1.44 1.42 1.41 1.41 1.40 1.39 1.38 1.36 1.36 1.34 1.33 1.32 0.02

-5

10

15

20

25

30

35

40

45

50

55

60

77.45 CDCl3 77.13 CDCl3 76.81 CDCl3

Alkyl-Bromide-X.13.fid Alkyl-Halide-I-C13

53.46

25.87 25.15

37.58

9000

8000

7000

6000

5000

4000

3000

A C

2000

1000

-1000 210 200 190 180 170 160 150 140 130 120 110 100 90 f1 (ppm) 80 70 60 50 40 30 20 10 0 -10

8.0 Alkyl-Bromide-Y.1.fid Alkyl halide C 7.5 7.0 6.5 6.0 5.5 5.0 4.5

1.00

4.0 3.5 f1 (ppm) 3.0 2.5 2.0

B C

EF

1.5 1.0 0.5 0.0 -0.5

1.18 4.02 1.04 0.97

0.25 3.02

4.18 4.17 4.17 4.16 4.16 4.15 4.14 4.14 4.14 4.13 4.12 4.12 1.88 1.86 1.85 1.85 1.84 1.84 1.83 1.83 1.82 1.82 1.81 1.80 1.79 1.78 1.77 1.75 1.75 1.74 1.74 1.73 1.73 1.72 1.71 1.70 1.70 1.69 1.68 1.58 1.57 1.57 1.56 1.56 1.55 1.55 1.55 1.54 1.54 1.53 1.53 1.52 1.51 1.51 1.50 1.48 1.46 1.46 1.45 1.45 1.44 1.44 1.43 1.43 1.42 1.41 1.41 1.40 1.06 1.04 1.02 0.95 0.93 0.91 0.00

20

40

60

80

-20

100

120

140

160

180

200

220

240

260

280

Alkyl-Bromide-Z.1.fid Alkyl-Halide-H

7.5 7.0 6.5 6.0 5.5 5.0 4.5

4.0 3.5 f1 (ppm) 3.0 2.5 2.0 1.5 1.0 0.5 0.0 -0.5 0 5 -5 10 15 20 25 30 35 40 45 50 55

B,C

0.70 3.88 1.98 1.21 1.96

0.84 0.05

4.50 4.49 4.48 4.47 4.46 4.46 4.45 2.19 2.16 2.16 2.15 2.14 2.14 2.13 2.12 2.12 2.11 2.10 2.10 2.09 2.09 2.08 2.08 2.07 2.06 2.06 2.06 1.98 1.97 1.96 1.95 1.95 1.94 1.93 1.93 1.92 1.91 1.91 1.90 1.89 1.89 1.88 1.87 1.86 1.85 1.84 1.83 1.83 1.82 1.81 1.80 1.80 1.79 1.72 1.71 1.70 1.70 1.70 1.69 1.69 1.68 1.68 1.67 1.67 1.67 1.66 1.66 1.65 1.64 1.42 1.40 1.39 1.38 1.37 1.07

60