Chem LLZA, Fall?:OLZ, NMR Worksheet # 3

GSULab Section

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

L"ffffirff,il}*utq what muhipticity is expected for each resonance? lossume thot the R sroups do not containhydragcn otomsthatcon Cpluplets A, B, orQ-

i{otatlon Ereraph: The fslloryirry spllttingtree predicts the apparance of multlplet B lf J1g = 6 Ht and Jgc= 5 Hr:

b. Draw a splitting tree to predict the appearance of multi&t B lf lp = 10 Hz and Js6 = 4 Hr. Drsw the spHtting Jp flrs, theneach splittingJx:

{a i -

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

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

I''1

;

..

i'-.

l

C: +rrylc.f

b. Zoom in on the multiplet centered near 2.2 ppm. This multiplet can be described as two overlapping triplets. Explain why thisis 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,c, Sketch a picture of the multiplet shape from part b in the space below, and then label it with letters (from the structure oftrimyristin)to indicate which triplet is which.

il ,,D'

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

Ha tottrl. te Ll1'dw'r tly on lq A'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 B do appear different. Propose an explanationfor this observation.

Fro-n /0ro"l TtrVu,hvt, lft an rln*k2^) ( tklu'L*l

'"t'l lh*/ )\zl*'zts

d,htkna u FL ,! it tvo C- a-"g h c Ly, tk^r* t r A'4Js),

f. Use 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 theunits field). Copy the peak yalues {in Hz} above each of the peaks in the picture below. Next, construct a splitting tree aboveeach multiplet to show why each is considered a doublet of doublets.

$o.rq\L'r --r>:>"tdl1

\.:-$.>c{

I

\.f.ri-_a,:r-.YI

14utsn6I

.R$.'t{Jc6

t

rypXHe( t-{1l

4.29 4.27 4.25 4.29 4.21 4.19 417 4.15 4.13 4.11 4.09 4.O7Chemical Shift (ppm)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: JSbl,lJ- 1557, \]6.1 Hz: ll b7,\ 0- Aq bl,7811'e Hz: fr 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 suchprogrirm is available on the following website: htto://www.colbv.edu/chemistrv/NMR/first.html Using this proSram and thecoupling constants 4.2 and 6.1, the following multiplet shape was predicted for the hydrogen labeled C in the previousdiagrams. (Try it yourselfl) Wo* backwards from this prediction to sketch a splltting tree in the space abwe it which showshow 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 distlnctpeaks). Zoom in on this region of the spectrum to examine the peak. Then sletch the obsenrcd muhlplet superimposed on theprediction below to show how the prediction corresponds with the observed shape, Then erqlaln your sketch in 10 words orless.

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 lastweek.

a. for each strudure, label the positions wlth letters to indicate which hydrogen atoms are magnetically different from eachother. 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 arepredicted, please draw the hydrogen atoms explicitly. Otherwise, you may use the abbreviation shown below in which thehydrogen 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 isexpected, also predict the "apparent" multiplicity (what would be observed if all of the vr'crnol coupling constants were identicaland no geminol coupling was observed.)

integral multidicity apparent muttiplicityif allJ valuea equal

DB,/-\. ...8r

ECA

A2B2c2D2E3

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

A' IB: I(=lP=3. IFslbr3/4.-II' Ll(z L

JltttNlA,Ll )-Ill/ad/.)Lo/-Au*

a,pltt*nl ,ex kl,a77a.a* C u."ft,^l f

*r X*n*?':t

orVT^r*/

integral multiplicity apparent multiflicityif all J values equal

Hg zA3!y"th Hp/1ree=?

Br'

5

5.

Br

dh'IB,'7Lr&Q= )"

f ; LadAddl

dd - "Ff.tt,ltvllll/ ' ,fp fw+,ktAliA -

elq gr,uutz-l

A')9rlCrlDrlF--lF"lh.l

IJd ttl//t /

/ liliJl)t/tdldil

iW:, ::: ii] arvarea*t'*vte+

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

:

- W: g-utl+f' rf g u'"ful

ayp. *oYltlelP / n".4:i/ /,T[;AlP Z UIH:"lp, kyl+f^Pf L**n'

Hl, ArL /tlr- B=3 tt apfa

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 lltflrst, then the splitting J4s:

= YHzi*tl .foH;

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

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

&e= {tt*_

d

d6a=\H-

ratdy Eo*L 1,otta5 a/a t|l,th\ H, ** th

-0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.0f1 (ppm)

0.0E+00

5.0E+07

1.0E+08

1.5E+08

2.0E+08

2.5E+08

3.0E+08

3.5E+08

4.0E+08

4.5E+08Alkyl-Bromide-T.1.1.1rAlkyl-Halide-J

6.01

3.01

6.00

1.72

1.73 H

DO1.7

4 HDO

2.09

2.09

2.10

2.11

2.36

2.37

A

B

C,D

-0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.0f1 (ppm)

-50

0

50

100

150

200

250

300

350

400

450

500

550

600

650

700

750Alkyl-Bromide-U.1.fidAlkyl-Halide-G

9.00

2.03

1.04

1.04

1.05

1.05

3.27

A

B

-0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.5f1 (ppm)

-50

0

50

100

150

200

250

300

350

400

450

500

550

600

650

700

750Alkyl-Bromide-V.1.fidAlkyl halide D

6.16

4.12

1.00

1.02

1.02

1.04

1.06

1.79

1.81

1.82

1.84 H

DO1.8

41.8

51.8

61.8

71.8

81.8

91.9

01.9

1

3.91

3.92

3.93

3.93

3.94

3.95

3.95

3.96

3.97

A

B

C

-0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.5f1 (ppm)

-50

0

50

100

150

200

250

300

350

400

450

500

550

600Alkyl-Bromide-W.1.fidAlkyl halide E

6.01

1.09

1.00

2.00

1.02

1.02

1.02

1.03

1.04

1.04

1.62

1.62

1.94

1.94

1.96

1.96

1.97

1.98

1.98

1.99

1.99

1.99

2.01

2.01

3.30

3.30

3.31

3.31

A

B

H2O

C

-0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.5f1 (ppm)

-5

0

5

10

15

20

25

30

35

40

45

50

55

60

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

3.07

1.05

4.06

2.00

1.00

0.02

1.32

1.33

1.34

1.36

1.36

1.38

1.39

1.40

1.41

1.41

1.42

1.44

1.44

1.45

1.55

1.56

1.57

1.58

1.58

1.60

1.61

1.62

1.63

1.74

1.76

1.78

1.79

1.79

1.80

1.82

1.83

1.84

1.84

1.85

1.86

1.88

1.89

2.13

2.14

2.15

2.16

2.17

2.18

2.18

2.19

2.20

4.18

4.19

4.20

4.21

4.22

4.23

4.23

4.24

A

B

C,D

E

F,G

-100102030405060708090100110120130140150160170180190200210f1 (ppm)

-1000

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

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

25.15

25.87

37.58

53.46

76.81

CDC

l377

.13 C

DCl3

77.45

CDC

l3

A

B

C

D

-0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.0f1 (ppm)

-20

0

20

40

60

80

100

120

140

160

180

200

220

240

260

280Alkyl-Bromide-Y.1.fidAlkyl halide C

3.02

0.25

0.97

1.04

4.02

1.18

1.00

0.00

0.91

0.93

0.95

1.02

1.04

1.06

1.40

1.41

1.41

1.42

1.43

1.43

1.44

1.44

1.45

1.45

1.46

1.46

1.48

1.50

1.51

1.51

1.52

1.53

1.53

1.54

1.54

1.55

1.55

1.55

1.56

1.56

1.57

1.57

1.58

1.68

1.69

1.70

1.70

1.71

1.72

1.73

1.73

1.74

1.74

1.75

1.75

1.77

1.78

1.79

1.80

1.81

1.82

1.82

1.83

1.83

1.84

1.84

1.85

1.85

1.86

1.88

4.12

4.12

4.13

4.14

4.14

4.14

4.15

4.16

4.16

4.17

4.17

4.18

A BC

D

EF

G

-0.50.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.5f1 (ppm)

-5

0

5

10

15

20

25

30

35

40

45

50

55

60

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

0.05

0.84

1.96

1.21

1.98

3.88

0.70

0.28

1.00

1.07

1.37

1.38

1.39

1.40

1.42

1.64

1.65

1.66

1.66

1.67

1.67

1.67

1.68

1.68

1.69

1.69

1.70

1.70

1.70

1.71

1.72

1.79

1.80

1.80

1.81

1.82

1.83

1.83

1.84

1.85

1.86

1.87

1.88

1.89

1.89

1.90

1.91

1.91

1.92

1.93

1.93

1.94

1.95

1.95

1.96

1.97

1.98

2.06

2.06

2.06

2.07

2.08

2.08

2.09

2.09

2.10

2.10

2.11

2.12

2.12

2.13

2.14

2.14

2.15

2.16

2.16

2.19

4.45

4.46

4.46

4.47

4.48

4.49

4.50

A

B,C

D

E