molecular parameters are known. • Studies can be made of the effects of changes in molecular weight dis tribution and for determining molec ular weight ranges required to achieve a desired performance.
Six- and seven-membered rings protonated efficiently When cyclohexenes and cycloheptenes are irradiated in hydroxylic media, such as alcohols, water, or acetic acid, the six- and seven-membered rings un dergo efficient protonation. Dr. Paul J. Kropp, head of the photochemical group at Procter & Gamble's Miami Valley Laboratories, near Cincinnati, Ohio, revealed a method for selectively protonating cyclohexenes or cyclohep tenes in the presence of exocyclic, acyclic, or larger-ring cyclic olefins at the American Chemical Society's Mid west Regional Meeting, in Columbia, Mo. The method will become useful for syntheses, he says, at least to prepare fine organic chemicals. There are five aspects of the reaction which have very strong synthetic potential: • Water, methanol, acetic acid, and other hydroxylic media can be added efficiently across a carbon-carbon dou ble bond. The reactions also take place under acid conditions, but are difficult to drive to completion. • Cyclohexenes and cycloheptenes can be converted to cycloalkyl alcohols, ethers, and acetates, for example, un der neutral conditions. Some cyclic olefins are acid sensitive, breaking down to acyclic compounds. • A double bond in a six- or sevenmembered ring can be selectively pro tonated in the presence of a second double bond not in the ring—in an acyclic side chain for instance. This selectivity is generally not possible with acid-catalyzed reactions. • While kinetically controlled, the reaction generates and traps carbonium ions. Thus, stereoisomeric prod uct ratios represent kinetic rather than thermodynamic properties. • With appropriate photosensitizers, 1-alkylcyclohexenes and -heptenes are converted to their exocyclic forms. This converts endocyclic olefins to their thermodynamically less stable exocy clic isomers. These, being acyclic ole fins, are photochemically unreactive. Since olefins absorb ultraviolet light efficiently only at low wave lengths (about 2000 Α.), photosensitizers must be used for this protonation. ( In photosensitization, light is absorbed by a donor molecule which transfers its triplet excitation energy to the ole fin.) Benzene, toluene, and xylene have been used as photosensitizers
CH3OD
J
.OCHa
ο
Ρ
Protonation reaction Cyclohexenes, cycloheptenes only
for the cyclohexenes and cyclohep tenes to generate the π-π* triplet ex cited state. The photosensitized protonation of cyclohexenes and cycloheptenes pro ceeds by an ionic mechanism, Dr. Kropp says. This has been supported by labeling studies [/. Am. Chem. Soc, 89,5199 (1967)]. Recent work by Dr. Kropp shows that cyclopentenes and norbornenes undergo radical-type reactions with similar photochemical conditions. Hence, the protonation reaction is spe cifically limited to six- and seven-mem bered ring systems. Also, Dr. Kropp has shown that the reaction proceeds much more rapidly if less than 1 % sul furic acid is added to the reaction mixture. The extra amount of availa ble hydrogen ions enhances the rate. This reaction is presently being used in the synthesis of sesquiterpene nat ural products by Dr. James A. Mar shall of Northwestern University. Dr. Marshall and a collaborator, Dr. Myron Pike, have been able to effect the pho tochemical isomerization of an endo cyclic tertiary allylic ether to the exo cyclic position in the synthesis of β-agarafuran. Such an isomerization would be impossible conventionally because of the high lability of such ethers.
AC3 may expand its scope to include action with advice The Advisory Council on College Chemistry (AC 3 ) may expand its ac tivities to become an action group as well as an advisory group. Such a move, suggested at the council's semi annual meeting held at American Chemical Society headquarters in Washington, D.C., would mean a basic policy change in AC 3 . At the least, it would be an added aim. Although the council has been strictly advisory up to now, Dr. C. C. Price of the University of Pennsyl
vania, first chairman of AC 3 , thinks it might be time to consider moving to ward implementation of specific proj ects. It might be well, he says, to set up ad hoc committees with definite council-approved objectives and defi nite time scales appropriate to a proj ect. Such a group would be responsi ble for completion of a project, either by doing the job itself or getting some group or individual to do it. To help guide the council through possible changes, chairman L. Carroll King of Northwestern University ap pointed an ad hoc committee. Dr. L. O. Morgan of the University of Texas, Dr. Richard W. Ramette of Carleton College, and Dr. Douglas A. Skoog of Stanford University were ap pointed from the group of new council members and were charged to evalu ate all aspects of the council and its activities and to recommend whatever reshaping of the council seems advisa ble. Among the ad hoc committee's func tions (initially suggested by Caltech's Dr. Harry Gray) will be to consider long-range aims and goals of the coun cil. Specifically, it will examine pres ent committee structure and the size of the council itself. Some council members feel that a 15-member coun cil, about half the present number, would be more manageable. The ad hoc committee will ask out side help to evaluate the effectiveness of the present council. Particularly, it will consult with these other new members of the council: Dr. Francis T. Bonner, State University of New York at Stonybrook; Dr. Charles F. Curtiss, University of Wisconsin; Dr. Milton Orchin, University of Cincin nati; Dr. Robert W. Parry, University of Michigan; and Dr. Arden L. Pratt, State University of New York at Al bany. The ad hoc committee will be gin its work at once so that recommen dations can be made before a proposal is submitted to the National Science Foundation next year for continued financial support of the council. When the council was first estab lished about five years ago, it was set up to identify problems in undergradu ate chemical education and to stimu late others in colleges and universities to solve the problems. AC 3 is an inde pendent group of academic chemists interested in achieving improvement and innovation in undergraduate chem istry curriculums and instruction at the national level. One of a group of col legiate commissions supported by NSF, AC 3 collects and disseminates infor mation through the activities of stand ing committees on freshman chemistry, curriculums and advanced courses, teaching aids, teacher development, science for nonscience majors, twoyear colleges, and resource papers. NOV. 13, 1967 C&EN
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