Name________Key __________________ 216 H W11-Exam No. 1 Page 2

I. (30 points) Treatment of 18.3 g of acid chloride 1 (Mw 182.5) with 16 g of aluminum chloride (AlCl3; Mw 133.3) at 0 °C resulted in, upon acidic work-up, the formation of 11.7 g of compound 2 (C10H10O). Note: Mw refers to a molecular or formula weight.

AlCl3H3O+-work-up

0 °C ;

1

2 (C10H10O)Cl

O

(1) (a) (3 points) What is the limiting reagent in this synthesis of 2 from 1? Show your work. 1: 18.3/182.5 = 0.100 mol AlCl3: 16/133.3 = 0.120 mol → acid chloride 1 is the limiting reagent (b) (3 points) What is the theoretical yield (by weight) of 2? Show your work. Mol weight of 2: 146 (g/mol) 0.1 mol x 146 g/mol = 14.6 g Answer: 14.6 g (c) (2 points) What is the percent yield of 2 in this experiment. Show your work. 11.7/14.6 x 100 = 80.1% Answer: 80% or 80.1% (2) (12 points) Compound 2 (C10H10O) has the following spectroscopic properties: IR (liquid film): 3067, 3024, 2945, 2878, 2835, 1683 (strong), 1602, 1597, 1483, 1455 cm-1 [no peaks in the 4,000-3100 cm-1 region]; 1H NMR (100 MHz, CDCl3) δ 2.12 (2H, apparent quintet, J = 6.6 Hz), 2.63 (2H, apparent triplet, J = 6.6 Hz), 2.93 (2H, apparent triplet, J = 6.6 Hz), 7.21 (1H, d, J = 8.5 Hz), 7.33 (1H, apparent triplet, J = 8.5 Hz), 7.46 (1H, apparent triplet, J = 8.5 Hz), and 8.01 ppm (1H, d, J = 8.5 Hz); 13C NMR (CDCl3) δ 23.3, 29.6, 39.1, 126.5, 127.1, 128.8, 132.7, 133.3, 144.4, and 197.8 ppm.

Draw in the box below the structure of compound 2 and assign all H peaks and the 13C peak at 197.8 ppm by writing their chemical shifts right next to the corresponding nuclei.

structure of 3: 4 points1H NMR assignments: 7 points13C NMR assignment: 1 point

OHH

HH

H HHH

HH

2.12 ppm

2.63 ppm*

2.93 ppm**These maybe reversed.

8.01 ppm

7.46 ppm

7.33 ppm

7.21 ppm

198.7 ppm

(3) (10 points) Draw in the box below a step-by-step, curved-arrow mechanism for the formation of 2 from 1 with AlCl3. You need not to show the formation of the AlCl3 complex of the resulting product or the acid-work-up step of the AlCl3 complex.

AlCl3

1

Cl

O

10

AlCl3Cl

O

O OHCl3Al Cl

O

Or simply Cl

mechanistic arrows: 1 pt eachintermediate: 2 pts each

Name_________Key_________________ 216 H W11-Exam No. 1 Page 3

II. (10 points) Draw in each of the boxes below the expected reaction product or intermediate.

AlCl3

H3O+-work-up

0 °C ;O

Cl

OCH3

H

C18H18O2

NHOH OH

OO

Δ

3

Cs2CO3CH3I50 °CDMF

1.

2. H3O+

β−alanine

acid workup

(2)

(1)

3

4

OH

O

OCH3

O

H

OOH

OO

OCH3

O

III. (12 points) The goal of recrystallization is to obtain purified material with a maximized recovery. For each of the following items listed, give an explanation in the boxes provided as to why this goal would be adversely affected. Each answer must be given in less than 20 words. (1) In the initial dissolution step, an unnecessarily large volume of solvent is used.

"lower recovery": A large amount of the compound should still be dissolved in the solution.

(2) The crystals obtained after filtration are not washed with fresh cold solvent before drying.

"lower purity": Impurities would still be adhered to the surface of crystals.

(3) The crystals referred to in (2) are washed with fresh hot solvent.

"lower recovery": Crystals collected would be dissolved.

(4) Crystallization is accelerated by immediately placing the flask of hot solution in an ice-water bath.

"lower purity": When crystallization is forced, impurities would be trapped in the crystal lattices and would not be remved by suction filtration.

Name____________Key______________ 216 H W11-Exam No. 1 Page 6 VI. (19 points) On the basis of its spectroscopic information provided below, answer the questions given on page 7, and propose the structure of the compound (C10H12O2). In the boxes on page 7, draw the proposed structure and assign all 1H and sp3 13C NMR peaks by writing each of the chemical shifts next to the corresponding H(s).

Name__________Key________________ 216 H W11-Exam No. 1 Page 7 VI. (continued) (1) (1 point) What is (are) units(s) of unsaturation of this compound? ______5________

(2) (2 points) What do these sp3 1H peaks in the 1 – 3.2 ppm region tell you in terms of the presence of an alkyl group in this molecule? ______Ethyl group_or_CH3CH2____

(3) (2 points) What does the 3H singlet peak at 3.83 ppm in the 1H NMR peak tell you in terms of the presence of an O-containing functional group in this molecule? ____ROCH3_or_R-C(=O)OCH3____

(4) (2 points) What does a pair of doublets in the 6.8 – 8.1 ppm region tell you in terms of the substitution pattern of the benzene ring? __para_or_1,4-disubstituted benzene ring______

(5) (2 points) What does the 13C NMR peak at 199 ppm tell you in terms of an O-containing functional group in this molecule? __ketone or aldehyde_______

(6) (2 points) What is the structure of thiscompound. Draw the structure in the box below.

(7) (8 points) Assign all 1H and sp3 13C chemicalshifts to the structure in the box below.

CH3OO

CH3OO

HH

H H H H H

HH

7.9 ppm

7.9 ppm6.9 ppm

6.9 ppm

3.8 ppm

2.9 ppm1.2 ppm

32 ppm9 ppm

56 ppm