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Honor Pledge (sign)_____________________________ Student Name:____________________________ (please print) Chemistry 232 Blackstock
FINAL EXAM
May 5, 2004
This exam contains 9 pages. Please check to see that your exam is complete. Write all answers on the exam and
show your work clearly. Partial answers, if worthy, will receive partial credit.
problem points
- some basics ______ (37 pts)
- Organic Structures and Terminology ______ (32 pts)
- General Knowledge (part 1) ______ (34 pts)
- General Knowledge (part 2) ______ (27 pts)
- Reactions (part 1) ______ (20 pts)
- Reactions / Mechanisms ______ (22 pts)
- Mechanisms (part 2) ______ (18 pts)
- Synthesis ______ (20 pts)
TOTAL ______ (210 pts) (10 pts extra credit)
HAVE A GREAT SUMMER
- Some Basics (37 pts)
(a) (4 pts) Circle the complete sets of any π conjugated atoms (of length ≥ 3 atoms) in the molecules below.
CN
O H 3 C
C CH 3
NO 2
(b) (4 pts) Write the organic reactant(s) and conditions needed to prepare the product below.
O
via Mixed Aldol
(c) (4 pts) Identify the hybridization level of the indicated atoms in the molecule to the right and give the HOMO and LUMO orbital types for this molecule.
CH 3 LUMO =
HOMO =
(d) (10 pts) Circle the π electron donating groups and underline the π electron withdrawing groups listed below.
-NO 2 -CHO -OC(=O)CH 3 -Cl -C(=O)CH 3
-CH 3 -CH 2 -CH 2 -CN -OCH 3 -N(CH 3 ) 2 -CN
(e) (6 pts) Hydration of formaldehyde is an example of one of the most common reactions of aldehydes and ketones. This reaction is (fill in the blanks) ___________________ addition to the ______________ group. Plea se write the two steps of hydration of formaldehyde below (use neutral conditions) using e- pushing arrows for t he first step and include the structures of the intermediate and product formed.
(f) (4 pts) Show below all the important resonance structures (there are 4) for the intermediate cation formed
upon para addition of "CH 3 CH 2 +" addition (as in F/C alkylation reaction) to anisole (methoxybenzene).
(g) (5 pts) Write the resonance structures and pi MOs for allyl anion (C 3 H 5 -) showing relative orbital energies, labels, occupancy, and spatial pictures.
- GENERAL KNOWLEDGE (61 pts) (a) (17 pts) Assign the reaction names (by numeral) to the appropriate functional group transformations:
Names Transformations
A. Diels-Alder reaction _____ alcohol to ketone
B. Reductive amination _____ ketone to methylene
C. Claisen condensation _____ 1-C elongation of an aldose
D. Jones oxidation _____ ester to β-keto ester
E. Hofmann rearrangement _____ dienes & olefins to cyclohexenes
F. Clemmenson reduction _____ formation of substituted acetic acids
G. Sandmeyer reaction _____ formation of amines from aldehydes or ketones
H. Gabriel synthesis _____ synthesis of aryl ketones
I. malonic ester synthesis _____ ketone to α,β-unsaturated ketone
J. Kiliani-Fischer synthesis _____ amide to amine with loss of 1-C
K. Hoffmann elimination _____ reaction of an aryldiazonium ion
L. Friedel-Crafts acylation _____ sodium nitrite in acid
M. Wittig reaction _____ alpha bromination of carboxylic acids
N. Aldol condensation _____ synthesis of 1˚ amines from phthalimide
O. diazotization _____ amide reduction (with no C loss)
P. Hell-Volhard-Zelinskii reaction _____ olefin synthesis by addition reaction
Q. LiAlH 4 _____ olefin synthesis by elimination reaction
(b) (5 pts) True or False (Circle T or F )
i. A carboxylic acid carbon is more highly oxidized than an aldehyde carbon. T F
ii. The two Kekule forms of benzene are in equilibrium with each other. T F
iii. Benzene is less reactive toward catalytic hydrogenation than is cyclohexene. T F
iv. Esters are more reactive than aldehydes toward nucleophiles. T F
v. Ketones are more acidic than esters and esters are more acidic than amines. T F
(c) (12 pts) Draw the structure of acetone, ethanol, methyl acetate, malomic ester, diisopropylamine, and acetic acid above the correct pKa for each compound.
pKa = 16 19 25 5 9 40
(d) (2 pts) Phenol is (circle one) MORE or LESS reactive than benzene toward electrophilic aromatic substitution?
(e) (10 pts) Write reactants and conditions needed to achieve the reactions indicated below. i
O^ by conjugate addition
ii
by Diels-Alder reaction O
O
O
iii
O (^) by acetoacetic ester synthesis
iv
by Witting reaction
v
OEt
O (^) O
via Dieckmann Condensation
(f) (2 pts) According to Huckel’s rule, a molecule news how many electrons in a cyclic conjugated pi system to
be aromatic? _______
(g) (6 pts) Of the following, circle the aromatic molecules, box-in the anti-aromatic species, and do not disturb molecules which are neither aromatic nor anti-aromatic.
N H
Br
H
(h) (4 pts) Draw the most stable chair form ofα-D-glucopyranose and circle the anomeric carbon. (show stereochemistry
(i) (3 pts) Provide a short reaction sequence to convert 3-pentanone to ethyl vinyl ketone.
(i)
O (1) LDA
(2) Cl
(j) OH
O
(1) MeMgBr
(2) H+, H 2 O, F-
(CH 3 ) 3 Si-Cl
(k)
CO 2 H
SOCl 2 (CH 3 CH 2 ) 2 CuLi
(l)
O
NaCNBH 3
ethanol
(m)
O HO 2 C CO 2 H ∆
- MECHANISMS (26 pts) (a) (8pts) Provide the key intermediates in the boxes & brackets for the following Curtius rearrangement.
Cl
O
NaN 3
acyl azide
H 2 O, ∆
acyl nitrene isocyanate
carbamic acid
NH 2
H 2 O
-CO 2
(b) Provide stepwise mechanisms for the transformations given below and include electron pushing for all steps except simple proton transfers.
(i) (6 pts) HNO 3 , H 2 SO 4 NO 2
(ii) (6 pts)
Cl
O
MgBr
OH
Ph Ph
(iii) (6 pts) (aldol reaction)
O
H
NaOH, MeOH H
OH O
