any 1.......plz help!
1) How can you account for the fact that glucose reacts with the Tollens reagent
to give a silver mirror, but glucose "-methyl glucoside does not?
2) Reaction of R-2-butanol with chromic acid (H2CrO4) and then with NaBH4
produces what product(s). What stereochemistry does(do) the product(s)
have(has)? Is it optically active? Fully explain your answer.
3) Two compounds with the same molecular formula have entirely different
boiling points. One of these compounds, ethanol (CH3CH2OH) has a boiling
point of 78.5 °C. The other compound, dimethyl ether (CH3OCH3) has a
much lower boiling point (i.e., !25 °C). Fully explain this.
4) Treatment of bromoacetone with ammonia yields a compound having the
formula C6H10N2 rather than the expected 1-amino-2-propanone. What is a
likely structure for the product and how do you explain the reaction?
5) Glycogen, the storage form of glucose in animals; whereas, starch is the storage
form of glucose in various plants. With genetic information being so similar in
all life forms on this planet, why would there be these two different storage
forms of glucose in plants and animals?
6) Cellulose is a polymer of $-linked D-glucose units. Do you think there would
be an effect on the structure of cellulose if there were alternating L- and Dglucose
units instead of just D-glucose units? Fully explain your answer.
7) Histidine is an aromatic amino acid even though it has a total of 8 B electrons.
Is this reasonable? Fully explain your answer.
8) The amino acid arginine is the most basic amino acid found in proteins. It has
a guanidino group (shown in red below), which contributes to its basicity, and
the over all structure is shown below:
2
H2N!C!NH!CH2CH2CH2CH!C!O!H
2 * 2
NH NH2 O
Lysine is another basic amino acid and its ,-amino group, shown in red below)
contributes to its basicity.
H2N!(CH2)4!CH!C!O!H
* 2
H2N O
Arginine is much more basic than is lysine. How do you explain this?
9) The polynucleic acids, DNA and RNA, are very similar to each other. The two
differences are the reduction of the 2'-OH of the ribose moiety to produce the
deoxyribose moiety and the use of thymine in DNA in place of uracil in the
RNA. Explain why these two changes are important in the stability of DNA as
compared to RNA.
10) Cellular membranes are composed of various phosphatidic acids (i.e.,
diacylglycerol phosphates with the acyl groups being long-chained, saturated,
and unsaturated fatty acids). Explain why there must be unsaturated fatty
acids in the phosphatidic acids? Naturally occurring unsaturated fatty acids all
have the cis conformation.
11) Gentiobiose, a rare disaccharide found in saffron and gentian, is a reducing sugar and
forms only D-glucose on hydrolysis with aqueous acid. Reaction of gentiobiose with
iodomethane and Ag2O yields an octamethyl derivative, which can be hydrolyzed
with aqueous acid to give 1 equivalent of 2,3,4,6-tetra-O-methyl-D-glucopyranose and
1 equivalent of 2,3,4,-tri-O-methyl-D-glucopyranose. If gentiobiose contains a $-
glycoside link, what is its structure?
