© 2000 Prentice Hall. All rights reserved.

Dr. Glaser's "Chemistry is in the News"
To Accompany Bruice, Organic Chemistry, 3/e.
Chapter 17. Carbonyl Compounds II: Reactions of Carbonyl Compounds with Carbon and Hydrogen Nucleophiles; Reactions of Aldehydes and Ketones with Oxygen and Nitrogen Nucleophiles; Reactions of alpha,beta-Unsaturated Carbonyl Compounds.


For each of the following questions, please refer to the following article:
NATURAL VITAMINS HAVE MORE ANTIOXIDANTS THAN MAN-MADE.
by Mark Allison (Medical Tribune News Service, April 2, 1998)


Editorial Comments

"Why worry about a balanced diet?! I eat what I like and I take my vitamin supplements regularly!" -- Cool?

When you buy vitamin supplements you might consider the purchase of synthetically prepared substances or you may elect to go for the natural supplement. With the synthetically prepared substance you know what you swallow and you can be fairly sure that the substance is clean. The natural supplement is much less "clean" and there is no such thing as "the" natural supplement. There are all kinds of extractions and condensations possible and you are swallowing a mixture that is not completely defined. In fact, in some cases it is some of the inadvertant admixtures that provide for a better, a more complete or even a synergistic effect. The present article illustrates this interesting point.


Pertinent Text References
Chapter 17. Carbonyl Compounds II.
Chapter 17. Box on "beta-Carotenes".
Chapter 12.16-20. Ultraviolet and Visible Spectroscopy.
Chapter 24. Lipids. Sections 24.6 on Terpenes and 24.7 on Vitamin A.



Questions

Question 1: In the article it was said that natural antioxidants can be divided into three basic types. Which three types are these? In particular, does the article give any specifics about the membrane surface bound vitamins?

Answer 1: Water-soluble compounds such as vitamin C guard cells' interiors, while fat-soluble antioxidants like vitamin E and beta-carotene enter cell membranes. A third class of antioxidants found in plant extracts - but generally not in synthetic vitamins - is located on membrane surfaces.



Question 2: Beta-carotene is an example of the class of "carotenoids". Carotenoids are "terpenes" and, more specifically, they are "tetraterpenes". Look up the definition of "terpenes" and find out what a "tetraterpene" is.

Answer 2: Bruice 3/e, Chapter 24.6.



Question 3: beta-Carotene is synthesized via a synthetic route that contains a Wittig reaction in the key step. Review the Wittig reaction and the mechanism of this reaction and then write down the structures of the substrates to prepare beta-carotene in this way.

Answer 3: Bruice 3/e, Chapters 17.11 and 24.7.



Question 4: Beta-carotene is a precursor to Vitamin A. Find out about the structure of Vitamin A (textbooks, library, ChemFinder, web, ...) and recognize what chemical transformation have to be done to convert beta-carotene into Vitamin A.

Answer 4: Bruice 3/e, Chapter 24.7.



Chemistry & Society.
Question 5: All these diets ... "The Zone", "Atkins", the low-fat fad, ... all these food choices. And then all these choices about diet supplements. How is one to know what is right?? Eating habits affect people's health perhaps more than any other lifestyle choice. And they are "habits" and they can be changed. Yet, we are not trained to select the right foods. Doctors are not trained in nutrition and they aren't really prepared to make diet recommendations (other than "Eat less, exercise more" which is always true). Here is my provokative suggestion: "Nutriton Science" should be part of the core curriculum in school for everybody. I am dead serious. Reflect on the benefits of such a "nutrition science" requirement. Could it be cost-effective or even cost-saving?