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NMR/IR and Mass spec. practice

A. Provide a structure consistent with the given data in each case.

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B.

1. Predict the structure of the molecules given by the following spectral data: Mass spectrum:M

+ = 116

IR: weak absorption at 2190 cm-1

, medium absorption at 1600 cm-1

2. Predict the structure of the molecules given by the following spectral data: Mass spectrum: M+= 82

molecular formula: C5H6O, IR: 1690 cm-1

(strong) with a shoulder at 1626 cm-1

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C. Molecular formula: C2H5I, IR peaks: 2973, 2910 cm-1

D. Molecular formula: C3H7Br, IR peaks: 2966, 2937 cm-1

E. Molecular formula: C4H9Br, IR peaks: 2971, 2922 cm-1

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F. Molecular formula: C4H9Br, IR peaks: 2966, 2937 cm-1

G. Molecular formula: C4H9Cl, IR peaks: 2963, 2937 cm-1

H. Molecular formula: C5H10O2, IR peaks: 1745, 1238 cm-1

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I. Molecular formula: C5H10O2, IR peaks: 1738, 1248 cm-1

J. Molecular formula = C3H9N. IR: 3368, 3282, 2962 cm-1

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K.

L.

M.

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M.

N.

O.

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P.

Q, Predict the proton NMR spectra for the following structures or other presented

information:

R. Predict the approximate positions of all of the important absorptions in the IR spectrum of

this compound.

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S. Explain how IR and 1HNMR spectroscopy could be used to distinguish between these two

compounds. Be as specific as possible.

…………………………………………………………………………………………………………………………………………………………………………………………….

…………………………………………………………………………………………………………………………………………………………………………………………….

T.

Predict the approximate chemical shift position for each of the different hydrogens in the 1H-NMR spectrum of this

compound. And

Predict the multiplicity of each of the signals in the 1H-NMR spectrum of the compound in problem 3a. and

Predict the integral for each of the signals in the 1H-NMR spectrum of the compound in problem 3a.

…………………………………………………………………………………………………………………………………………………………………………………………….

…………………………………………………………………………………………………………………………………………………………………………………………….

V. Explain which functional group is present in the compound with the following IR spectrum.

Show a possible structure for the compound. C6H10

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W. The following IR spectrum is one of the four compounds shown below. Circle the correct

compound and briefly explain your choice.

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X. Show the structure of the ion that is responsible for the peak at m/z = 43 in the mass spectrum of 2-

heptanone.

Y. Show the structure of the ion that is responsible for the peak at m/z = 99 in the mass spectrum of 2-

heptanone.

Z. Explain how these isomers could be distinguished by mass spectroscopy.

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1) Calculate the average mass for these structures.

Match each structure to one of the following mass spectra.

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1. The molecular ion in the spectrum below is 58. What alkyl group was lost to form the intense fragment at

m/z 43?

a. methyl (CH3) b. ethyl (CH3CH2) c. propyl (CH3CH2CH2)

2. For this same spectrum, choose the compound that the spectrum represents

a. 2-methyl butane b. butane c. pentane d. cyclobutane e. 1-butene

.3. How many sets of equivalent hydrogen atoms are there for 2-propanol?

a) 2

b) 3

c) 4

d) 8

4. How many sets of equivalent hydrogen atoms are there for the following compound?

a) 3

b) 4

c) 5

d) 6

5. Which is the order of increasing δ values downfield from TMS for the methyl groups shown (lowest first)?

a) I, III, IV, II

b) II, I, III, IV

c) IV, II, III, I

d) III, IV, II, I

6. Which compounds show signal splitting in the 1H-NMR spectrum?

a) I, II

b) III, IV

c) I, III

d) II, IV