First Exam CHEM 256 – Organic Chemistry II Prof. Bastin

First Exam CHEM 256 – Organic Chemistry II

Prof. Bastin Spring 2014

Name ___________________________ Provide clear, concise answers using unambiquous, carefully drawn structures (where appropriate) for all of the questions. Good luck and enjoy!

1) _______/12 pts 2) _______/8 pts

3) _______/8 pts

4) _______/6 pts Total: ________/100 pts 5) _______/10 pts

6) _______/12 pts

7) _______/12 pts 8) _______/12 pts 9) _______/20 pts

Bastin – Exam #1 Chem 256 - Spring 2014

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1) (12 pts) Show how IR spectroscopy can be used to distinguish between the compounds in each set. Include all distinguishing peaks.

(a)

(b)

(c)

(d)

O

O

OH

O

O

and

O

and

and

andOH

OH

O

Bastin – Practice Exam #1 - Addendum Chem 256 - Spring 2014

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2) (8 pts) Identify the symmetrical relationship (homotopic, enantiotopic, diastereotopic) of the underlined atoms in the following molecules.

a)

b)

c)

d)

H3C CH3

H H

H3C

H H

CH3

H3C H

H

H3C CH3H

CH3H3C

CH3

H3C CH3


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3) (8 pts) For each of the following IR spectra (a-c) there is a choice of three possible types of compounds. For each spectrum, choose the most appropriate class of compound. Explain your reasoning by noting the presence or absence of characteristic bands in the spectrum.

a) 1-alkyne, symmetrical internal alkyne, or nitrile

b) primary amide, primary amine, or nitro compound


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4) (6 pts) Indicate the number of peaks that a (a) 13C-NMR spectrum and (b) 1H-NMR spectrum of each of the following molecules would contain? a)

b)

c)

H3C CH3


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5) (10 pts) Following are three compounds with the molecular formula C4H8O2 and three 1H-NMR spectra. Assign each compound its correct spectrum and assign all signals to their corresponding hydrogens.

O

O O O

O

H

O

(1) (2) (3)

10 5Chemical Shift (6)

5Chemical Shift (6)

5Chemical Shift (6)

13.16 Following are IH-NMR spectra for compounds D, E, and F, each with moiecu.":CuH,r. Each readily decolorizes a solution of Br, in CClr. Propose structural fc.::compounds D E, and F and account for the observed pattems of signal splitt: i

Unless othenrvise noted all art on this page @ Cengag: ,.-

l0

rlt,{ilIt

550


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6) (12 pts) Draw the product(s), if any, of the following reactions. Indicate stereochemistry where relevant.

a)

b)

c)

CH2I2Zn(Cu)

Br

1) Mg, ether2) O

3) H+

Br

Mgether


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7) (12 pts) Provide the structure of a compound with the molecular formula C4H8O using the IR and 1H-NMR provided below. Justify your structure by assigning ALL the appropriate peaks in the IR and NMR spectra and with a short narrative describing what structural information each piece of data provided.

Integration

2H 3H 3H


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8) (12 pts) Provide the structure of a compound with the molecular formula C3H6O2 using the IR, 1H-NMR, and 13C-NMR provided below. Justify your structure by assigning ALL the appropriate peaks in the IR and NMR spectra and with a short narrative describing what structural information each piece of data provided.

Integration 13C-NMR spectrum shows peaks at 14, 60, and 161 ppm

1H 2H 3H


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9) (20 pts) Devise (below and on the following blank page) a synthesis for the following transformations using any reagents that we have discussed, the indicated starting material, and any other stable organic starting materials needed. If you need more space, please use the back of this sheet and direct me there. For FULL credit be sure to show the retrosynthetic analysis AND the complete synthesis.

a)

from

OH


14

b)

from


15

degrees of unsaturation = (#C atoms) – (#H atoms)/2 + (#N atoms)/2 + 1


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Functional Group Frequency (cm-1) Intensity and Comments Alkanes

C–H C–C

2980-2850 1480-1420

medium to strong medium

Alkenes =C–H stretch =C–H bend C=C

3150-3000 980-960 (trans) 730-665 (cis) 1680-1600

medium; very weak for trans strong strong weak to medium

Alkynes ≡C–H C≡C

3350-3300 2260-2100

strong weak to medium

Alkyl halides C–Cl C–Br C–I

800-600 600-500 500

strong strong strong

Alcohols O–H C–O

3650-3300 1350-1050

strong and broad strong

Amines N–H C–N

3500-3100 ~1200

medium and strong; 1° amines-2 bands; 2° amines-1 band medium

Aromatics C–H stretch C–H bend C=C

3080-3020 900-730 1650-1580

weak to medium strong weak to medium

Carbonyls (C=O) Ketones/aldehydes Esters Amides Acids Acid Anhydride Acid Chlorides

1730-1700 1750-1735 1680-1630 1730-1700 1850-1740 1820-1770

strong strong; also has C–O stretch strong; 1° and 2° amides also have N-H stretch strong; also has O–H stretch strong; doublet strong

Nitrile (C≡N) 2200-2250 medium

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First Exam CHEM 256 – Organic Chemistry II Prof. Bastin