Showing papers in "Chemical Reviews in 1970"

Centrifugal effects in reaction rate theory

Abstract: Early theories of unimolecular reaction rates have considered the role of overall molecular rotations by using two ostensibly different approaches ; the results of both approaches are identical, however. Eyring1n2& postulated that all degrees of freedom of the reactants are in thermodynamic equilibrium with those of the activated complex (except that special considerations attach to that degree of freedom associated with the reaction coordinate). In this simple formulation, and without specific considerat of the conservation of angular momentum, rotationq contribute a factor to the high-pressure specific rate constant, kmuni, for a unimolecular reaction which is the ratio of the square root of the moments of inertia of the rotational partition functions of the activated complex and the molecule, i.e., (ZA+ZB+ZO+/ZAZBZC)’”. Another approach that was applied even earlier to a diatomic approximation for unimolecular decomposition reactions is that of Rice and Gershinowitz (RG).8 They pointed out that angular momentum conservation requires that the rotational quantum number does not change when the “activated complex” configuration at the top

The contraceptive progestagens.

Abstract: Progestagens used as antifertility agents in oral contraceptive agent (OCA) preparations are reviewed. The history of their development is briefly presented and the following groups of progestagens are revie wed with regard to structure and production: 1)the 19-norprogestagens; 2 ) 17 alpha-acetoxyprogesterone; 3)the 6-methylated progestagens; 4)chlor madinone acetate; 5)algestone acetophenide quinestanol acetate and norgestrel; and 6)other progestagens examined as contraceptive agents. Structural formulas of the various compounds accompany the discussions. Biologic activity classifies progestagens as: 1)progestagens without estrogenic and androgenic effects; 2)progestagens without estrogenic androgenic and antiandrogenic effects; 3)progestagens with slight androgenicity 4)progestagens with some androgenicity; 5)progestagens with some estrogenic and slight androgenic properties; and 6)estrogens with some progestational but no androgenic activity.