Download Homework Set #1

Homework Set #7
Chemistry 1315
Spring 2004
______Answer key_____
Name
Handed Out:
Due:
3-26-04
4-1-04 at 9:30am in class
Late Policy:
One day late (4-2-04 10am): 50% off
Two days late (4-3-04 10am): 75% off
After 10am 4-3-04:
no credit
You may work in groups of up to 3 students. However, each student must
make contributions to the answers.
Total:
Questions
Points possible
1
2
3
4
5
6
7
8
10
20
10
10
10
10
20
10
Your Score
100
1
Question #1 (10 points)
Draw beta-L-glucopyranose (cyclic beta-L-glucose) in its most
stable chair conformation. Label the substituents as axial or
equatorial.
OH
OH
O
Ring Flip HOH2C
O
OH
HO
CH2OH
OH
OH
HO
OH
Most stable, all
equatorial
2
Question #2 (20 points)
At equilibrium in aqueous solution, D-fructose consists of 70% betapyranose, 2% alpha pyranose, 23% beta furanose, and 5% alpha
furanose forms. Draw all four.
HOH2C
CH2OH
O
HOH2C
HO
O
OH
HO
OH
CH2OH
OH
OH
alpha Furanose
beta Furanose
CH2OH
O
HO
OH
OH
OH
O
CH2OH
OH
HO
HO
alpha Pyranose
HO
beta Pyranose
3
Question #3 (10 points)
The two stereoisomers (alpha and beta) of maltose (a disaccharide)
undergo mutarotation which means they interconvert into each
other. Based on your understanding of carbonyl and alcohol
chemistry, provide a mechanism that will account for this exchange.
OH
O
HO
OH
HO
HO
O
O
HO
O
OH
HO
HO
HO
O
HO
HO
O
OH
O
HO
OH
HO
HO
OH
O
HO
HO
OH
O
O
HO
OH
HO
HO
OH
H-Transfer
OH
HO
HO
HO
O
HO
O
HO
OH
HO
H-Transfer
O
OH
HO
HO
O
O
HO
OH
HO
4
Question #4 (10 points)
D-2-deoxyribose is found in DNA. Draw the structure. Deoxyribose
and ribose form esters with phosphoric acid in DNA and RNA. Can
both monosaccharides react to form the same number of ester
combinations? Show the reactive sites for esterfication.
CH2OH
O
OH
OH
2-deoxy-D-ribose
CH2OH
O
OH
OH
OH
D-Ribose
The reactive groups you need are alcohols or carboxylic
acid derivatives. You don't have any of the second class
but a number of alcohols. Ribose has one more, therefore,
it can undergo one more ester.
5
Question #5 (10 points)
Give the IUPAC name for the following carboxylic acids:
A)
H3C
CO2H
B)
H 2C
CH3
O
HO
C) H3C
a)
b)
c)
CO2H
trans-2-butenoic acid
2-methyl-3-propenoic acid
4-methyl-benzoic acid
6
Question #6 (10 points)
Predict the product from the reaction of phenylacetic acid with each
of the following reagents: a) KOH, b) SOCl2, c) LiAlH4 then H2O,
and d) CH3CH2OH, H+
a) the potassium salt
b) makes the acid chloride
c) the alcohol
d) the ethyl ester
7
Question #7 (20 points)
Outline a sequence of reaction(s) that will allow pentanal to be
converted into a) pentanoic acid, b) hexanoic acid, and c) 2-hydroxy
hexanoic acid.
Several possible ways. Here is an example:
OH
2-Hydroxy-hexanoic acid
Hydrolysis
H2O, HCl
CO2H
OH
CN
NaCN
H+
O
Jones Reagent
CrO3
O
Pentanoic acid
OH
LiAlH4
OH
HX
X
Grignard, Mg
MgX
CO2
H3O+
CO2H
Hexanoic Acid
8
Question #8 (10 points)
Describe two methods for the preparation of 5-methyl hexanoic acid
from 4-methyl-1-pentanol.
You have to remove the OH and add CO2H. There are a number of
ways to do this but the easiest are Grignard chemistry and nitrile
hydrolysis. To make life easy, transfer the alcohol into an alkyl
halide using some of the reactions we discussed in class or activate
the alcohol and make it a good leaving group. Then do Grignard
chemistry for one way to introduce CO2 or add CN and then
hydrolyze the CN to the acid.
9