Tutorial. lH Chemical Shifts and Conpling Constants;a

Purpose of the Lab

-Structure elucidation basing on the interpretation of lH spectra.

-Assignment of lH resonances. Effect of homodecoupling.

-Understanding the origin of the multiplicities of lH multipIets.

-Extract lH chemicaI shifts, geminaI (2JHH) and vicinal (3Jlffi) coupling constants.

This lab consists of t wo separate sections:

AA) Interpretation of lH spectra for organic compounds (pages Al -Ala)

,B) Interpretation of 1 H spectra of nucleosides (pages B 1 )

Note. All spectra have been calibrated using a reference signal. Chemical shifts therefore can

r-"e extracted directly from the multipIets.

(A) lH spectra of organic compounds.

In pages Al -A1O are presented the lH spectra of some organic compounds. The areas under all

relevant multipIets have been integrated.

(I) Phenyl ethanol in CDCI3 / CHCI3 : C6HS-CH2-CH20H (p. Al)

-Find the chemical shifts of all protons in the molecule. Justify.-Explain the multiplicities of the multipIets at 8 = 2.86 and 3.8 ppm. Which additional information can

be obtained from the analysis of these multipIets?

~ Which protons are magnetically equivalent?

(2) p-nitrophenylethanol in CDCI3 / CHCI3 : P-NO2-C6H4-CH2-CH20H (p. A2)

r Same questions as for (I).

(3) 2-amino, 5-NO2-toluene in CDCI3 / CHCI3 : 2-NH2' 5-NO2-C6H3-CH3 (p. A3)

-Which protons are magnetically equivalent? Find the chemical shifts for all protons. Which of the

aromatic protons is expected to resonate most downfield? most upfield? Explain w hy?

-Note: all signals marked by x are impurities or peaks belonging to the solvent.

(4) Vi,nyl acetic acid in CDCI31 CHCI3 (pp. A4 and AS):

H2C=CH-CH2-COOHp. A4 : coupled lH spectrum with expansions of each multipIetp. AS: Only the multiplet(s) at ö ~ 3.0 ppm has(ve) been decoupled. This means that the effect of

this(these) multiplet(s) (let's call it A) is eliminated from this spectrum, which should result in the

simplification of any hypothetical B multipIets previously scalar coupled to A. (compare the

expansions for the various multiplets in p.AS with those in p.A4).

-Assign the resonances, extract the chemical shifts and all ffi-I coupling constants.

(5) 2-hydroxyethyl-pyridine in CDCIJ / CHCIJ (p. A6): CSH4N-CH2CH20H

-Assign all resonances and justify your assignment, extract all In-I coupling constants.

Try to differentiate the different protons from the point of view of multiplicityand chemical

environment. Also consirler that long range In-I couplings are possible (i.e. 4 bonds, for instance if the

geometry of the HCCH fragment is weIl detined)

(6) Benzyl alcohol in CDC131 CHCI3: C6HS-CHlOH [p. A7(1)]

Assign all resonances. Consider only the integrals for each multipiet, not their multiplicities. The peakr-

dt 0.0 ppm is that of TMS.

(7) Dimethylformamide: (HJC)2N-CHO [p. A7(2)]

(8) Crotonaldehyde: CHJCH=CH-CHO [p. A8(1)]

(9) Diethylmalonate: CH2(COOEt)2 [p. A8(2)]

For each of :l'""'\

Assign all resonances. Consider only the integrals for each multipIet, not their multiplicities. The peak

at 0.0 ppm is that of TMS.

CH3

(10) 1,3-dimethyluracil [p. A9 (1)]

Assign all resonances.

r

(-.11) Indane [p. A9 (2)]

Assign all resonances.

H3C(12) 113-carene [p. AI0 (1)]

Assign all resonances.

(B) 1H spectra of a Ducleoside: CordycepiDo

NH2

NH5' H II HaJ-..;;:::::. N

\/5 ~ I

H O C>< °~ 2. ..N~N~

H~~'. ~-~ I..,'..

i H1,

OH

H2

Sample:I I

1-i3" I

I"""'

The lH spectrum of this compound in 99% D2O solution (D2O is used as the locking solvent) is

shown on p. Bl (see also also the expansions for all multipIets). Reference: DSS, 8,; 0.015 ppm

~ote that under the experimental conditions the NH2 protons as weIl as the hydroxy protons have

cxchanged with Deuterium from the solvent, so that theyare not observable on the spectrum.The spectrum has been recorded at Vo ,; 500.1325 MHz.

-MullipIets (or singlets) can be found at: ö = 8.33; 8.23; 6.08; 4.84; 4.64; 3.93; 3.72; 2.33 and 2.20

ppm. Bach of them corresponds to one proton.

-Find the chemical shifts of Hl', H2', H3', H3", H4', HS', HS", H2, H8 knowing that:

(a) HS" resonates downfield compared to HS"

(b) H3" resonates up field from H3'.

(c) H8 resonates downfield from H2.

(d) All signals marked with x are impurities.

r- (e) The strong signal at = S ppm corresponds to the residual HOD protons.

-' (1) Assume free rotation around the C4'-CS' bond.

(g) Upon decoupling of the proton at ö = 4.84 ppm, the following changes in the multiplicities

have been observed:" -ö = 2.33 ppm, the multipIet has been simplified to become a doublet of doublet

-ö = 2.20 ppm, the multipIet has been also simplified to become a doublet of doublet

(h) In a separate experiment, upon decoupling of the doublet at ö = 6.08 ppm, ONL y the

mullipIet at ö = 4.84 ppm has been simplified to become a doublet of doublet.

-Extract all :mI coupling constants from the multipIets.

~~~

E=:l'-

UQJo.In

:1:

~OCnJ.c

QJI

~>-CQJ

.co.

-r

Lncc

N,:-

~

.ttt,:-

6;"0",-,~~

tO66"t-

, 1-==

~~

~StOO.2--

~~06.0

,.

er g

l-,--:C:

~c:::, :-.t.s.:-.;.00:-

ccM

~

I'""""

-

Eo.o....

~

..

r-.

~

Ite.J6a~uI,.

~

~.I.K-...809(-

'L'LK-

.

-

(\

--O2L6.~---" " .

--L2EO.2

(R.J6aluI

~

.

~

!

MC\J

E=''-

uQ)a111

:1:-

Q)cQ)='

oI

C\JQ~I

In

Oc

eroI

(\J-

-60EO"E--wVwv w.=;

~06~L.~

~

o-N

~ ==-;..01'-

..IEaa

--OvOO.~--"F"" F

[1.91.-

Eo.o. "

~~;t20ltt-

~6;IEE-

'H

.-J ~~..

9!8!6.-.\186.-

;.!86.-06686.-

1;866.-

~~~

leJ5a1UIr..

~

.

~~

~ ~

~ ~

II

m

~

I

.~

..~

~ ~

r r

i ~ ~x

A

~

'--v

, ., I. ., , I' , , , I ,

ppm 5.85 5.80

v, , I' ., , I' ,

ppm 5.10

"'1""""'1""""'

ppm 11.9

, I' , , , I' .,

ppm 3.05

r

.

~

I

"',~

I

~

f"

, , , , , , , , I' , , , , , , , , I ,

ppm 11.9

, ., .I. , , .I' ., ,

ppm 5.85 5.80

, , , I' , , I

ppm 5.1U

~

(\

vinyl acetic acid. 8/1. 1H with

decoupling

~

~~~~

:::==. .., , : ' , ..:=1~

ppm 12 10 8 6 ~ 2

,

--E9~0.2

9L90"2

~

te.J5a1uI