Taft, Robert

Taft, Robert, The beginning of liquid ammonia research in the United... 

As in Europe, air pollution research activity expanded tremendously in the United States during these three decades. The headquarters of federal research activity was at the Robert A. Taft Sanitary Engineering Center of the PHS in Cincinnati, Ohio, during the early years of the period and at the National Environmental Research Center in Triangle Park, North Carolina, at the end of the period. 

As suggested by Roberts and Moreland many years ago (1953), the acidity constants of 4-substituted bicyclooctane-l-carboxylic acids provide a very suitable system for defining a field/induction parameter. In this rigid system the substituent X is held firmly in place and there is little possibility for mesomeric delocalization or polarization interactions between X and COOH (or COO-). Therefore, it can be assumed that X influences the deprotonation of COOH only through space (the field effect) and through intervening o-bonds. On this basis Taft (1956, p. 595) and Swain and Lupton (1968) were able to calculate values for o and crR. 

The National Institute for Occupational Safety and Health (NIOSH) conducts research on occupational diseases and injuries, responds to requests for assistance by investigating problems of health and safety in the workplace, recommends standards to the Occupational Safety and Health Administration (OSHA) and the Mine Safety and Health Administration (MSHA), and trains professionals in occupational safety and health. Contact NIOSH, 200 Independence Avenue, SW, Washington, DC 20201 Phone 800-356-4674 or NIOSH Technical Information Branch, Robert A. Taft Eaboratory, Mailstop C-19, 4676 Columbia Parkway, Cinciimati, OH 45226-1998 Phone 800-35-NIOSH. 

Finally, in this account of multiparameter extensions of the Hammett equation, we comment briefly on the origins of the a, scale. This had its beginning around 1956 in the a scale of Roberts and Moreland for substituents X in the reactions of 4-X-bicyclo[2.2.2]octane-l derivatives. However, at that time few values of o were available. A more practical basis for a scale of inductive substituent constants lay in the o values for XCHj groups derived from Taft s analysis of the reactivities of aliphatic esters into polar, steric and resonance effects . For the few o values available it was shown that o for X was related to o for XCHj by the equation o = 0.45 <7. Thereafter the factor 0.45 was used to calculate c, values of X from o values of XCH2 . ... 

Alkyl cations are thus not directly observed in sulphuric acid systems, because they are transient intermediates present in low concentrations and react with the olefins present in equilibrium. From observations of solvolysis rates for allylic halides (Vernon, 1954), the direct observation of allylic cation equilibria, and the equilibrium constant for the t-butyl alcohol/2-methylpropene system (Taft and Riesz, 1955), the ratio of t-butyl cation to 2-methylpropene in 96% H2SO4 has been calculated to be 10 . Thus, it is evident that sulphuric acid is not a suitable system for the observation of stable alkyl cations. In other acid systems, such as BFj-CHsCOOH in ethylene dichloride, olefins, such as butene, alkylate and undergo hydride transfer producing hydrocarbons and alkylated alkenyl cations as the end products (Roberts, 1965). This behaviour is expected to be quite general in conventional strong acids. 

Lipsett MJ, Carmelli D, Winship-Ball A, et al. 1982. Quantitative cancer risk assessment for occupational exposure to ethylene dibromide. Govt Reports Announcements Index (GRA I). Cincinnati, OH Robert A. Taft Labs. NTIS/PB83-184325... 

Brandt, C. S., and U. Holzel. Problems of the Recognition and Evaluation of the Effects of Gaseous Air Impurities on Vegetation. Robert A. Taft Sanitary Engineering Center Technical Report A61-37. Cincinnati U.S. Department of Health, Education, and Welfare, 1%1. 

National Institute for Occupational Safety and Health, Robert A. Taft Laboratories, 4676 Columbia Parkway, Cincinnati, OH 45226... 

Roberts269 has studied the hydrolysis of series of ethyl esters271 272 and alkyl benzoates273 in a limited range of water-dimethyl sulphoxide mixtures in some detail, and finds that the data for the hydrolysis of aliphatic ethyl esters (at 35°C in 85% dimethyl sulphoxide-water) fit the modified Taft equation (eqn. 5, p. 132). The values of p = 1.88 and 8 = 0.88 can be compared with p = 2.39 and 8 = 1.04 for 85% EtOH-water at the same temperature. The polar reaction constant is reduced in the dipolar aprotic solvent, consistent with a reduced degree of bond formation in the transition state, expected if the activity of the hydroxide ion is increased. However, Roberts considers that the sensitivity to steric effects, as measured by 8, would be reduced more substantially if bond formation were less advanced. It is difficult to accept this argument, since we... 

This chapter is dedicated to the memory of Robert Wheaton Taft (1922-1996). The contributor enjoyed friendship with Bob Taft for some thirty years. The present chapter, like the corresponding chapters in earlier volumes1-7, contains much discussion of Taft s work in linear free-energy relationships. Since the 1950s he had always been at the forefront of progress in this field. 

Another more arbitrary but equally reasonable technique is to choose a single reaction as a model typical of the processes under consideration. The results from study of this reference reaction then could be employed to define the parameters for the substituent groups in other similar reactions. Thus, Hammett (1940) selected the ionization equilibria for substituted benzoic acids in water as a reference reaction and Taft (1956) employed the ionization equilibria of 4-substituted bicyclo[2.2.2]octane-l-carboxylic acids (Roberts and Moreland, 1953) for evaluating the inductive e-constants. The constants so defined are invariant. The validity of this scheme is measured by the agreement between the predictions of the reference reaction and the actual systems under study. 

R. D. Schmidt, A Student remembers Robert. W. Taft , Chem. Intell., 1996, 2 (4), 52 and Newsletter of International Group for Correlation Analysis in Chemistry, No. 20, December 1996 deposited in RSC Library. 

Advanced Drug Formulation Design to Optimize Therapeutic Outcomes, edited by Robert O. Williams III, David R. Taft, and Jason T. McConville... 

Rein, Carlo Silipo, Robert W. Taft, Antonio Vittoria, Kent R. Wilson, and Michael C. Zerner. These scientists enriched the field of computational chemistry each in his own way. Three of these individuals (Almlof, Wilson, Zerner) were authors of past chapters in Reviews in Computational Chemistry. 

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