© 2000 Prentice Hall. All rights reserved.

Dr. Glaser's "Chemistry is in the News"
To Accompany Bruice, Organic Chemistry, 3/e.
Chapter 8. Reactions of Alkanes: Radicals.


For each of the following questions, please refer to the following article:
TOO MUCH VITAMIN C IS BAD FOR YOU, SAY EXPERTS
by Charles Arthur (The Independent, London, April 9, 1998)


Editorial Comments

Linus Pauling is famous for many things. In 1954, Pauling won the Nobel Prize in Chemistry for his research on the nature of the chemical bond. Laue, the Braggs (father and son) and Pauling employed X-ray crystallography to map the "static" nature of chemical bonds and greatly advanced bonding theory. In chapter 5 of the book "The Chemical Bond - Structure and Dynamics" (Ahmed Zewail, Editor, Academic Press 1992), Linus Pauling describes how he became interested in the chemical bond. He starts by saying, "My curiosity about the properties of substances developed early". Curious he was and his Linus Pauling Institute of Science and Medicine was a perfect device to follow up on this curiosity!

Perhaps Pauling is best known for his hypothesis that large dosages of vitamin C can do wonders for you, a thesis that he described in his 1970 book "Vitamin C and the Common Cold." Pauling himself took 18,000 milligrams of vitamin C a day which is 300 times the recommended daily allowance for adults (60 milligrams). It is the question of the usefulness of large quantities of vitamin C that is now being questioned by the British scientists.



Pertinent Text References
Chapter 8. Reactions of Alkanes. Radicals.
Chapter 10. Reactions at an sp3 Hybridized Carbon II. See stamp on the book's margin.
Chapter 20. Carbohydrates. See box on Vitamin C.
Chapter 23. The Organic Mechanisms of the Coenzymes. Metabolism.



Questions

Question 1: A molecular model of vitamin C can be found in the visualization center accompanying Chapter 8. Draw the structure of vitamin C and explain how ascorbic acid functions as antioxidant.

Answer 1: Oxidation of cellular materials produces radicals. Vitamin C acts as an antioxidant because it functions as a radical inhibitor. The enol H-atoms can be abstracted easily by radicals and the radical formed in the process is stabilized.



Question 2: What reagents cause oxidative stress?

Answer 2: Oxygen molecules, hydrogen peroxide, hydroxide radical, and others.



Question 3: Vitamin C and vitamin E (alpha-tocopherol) have somewhat complementary functions as radical inhibitors. Briefly explain.

Answer 3: Vitamin C is present in aqueous environment and vitamin E does the job in nonpolar membranes.



Question 4: Linus Pauling actually won two Nobel Prizes. Use online search facilities to find out when the second Nobel Prize was awarded and for what achievement.

Answer 4: 1962, Nobel Peace Prize, campaigned against nuclear weapons.



Chemistry & Society.
Question 5: I was about to comment on the credibility of Linus Pauling outside of the fields of his scientific expertise. Yet, in the course of my research, I came across the website of the Vitamin C Foundation0 and read th following quote by Linus Pauling (from a speech on December 10, 1954, speaking to a group of university students while in Sweden to receive his first Nobel Prize: "When an old and distinguished person speaks to you, listen to him carefully and with respect -- but do not believe him. Never put your trust in anything but your own intellect. Your elder, no matter whether he has gray hair or has lost his hair, no matter whether he is a Nobel Laureate, may be wrong. The world progresses, year by year, century by century, as the members of younger generations find out what was wrong among the things that their elders said. So you must always be skeptical -- always think for yourself."