scholarly journals THE ESTIMATION OF SOME 17-ALKYL-SUBSTITUTED STEROIDS WITH THE ZINC CHLORIDE – ACETYL CHLORIDE (TSHUGAEV) REAGENT AND A POSTULATED REACTION MECHANISM

1951 ◽  
Vol 29 (2) ◽  
pp. 217-222 ◽  
Author(s):  
R. H. Cox ◽  
E. Y. Spencer
Keyword(s):  
Reaction Mechanism ◽  
Acetic Anhydride ◽  
Sulphuric Acid ◽  
Zinc Chloride ◽  
Acetyl Chloride ◽  
Maximum Absorption ◽  
Ring Cleavage ◽  
Reaction Products ◽  
Experimental Support

The reactivity of a number of 17-alkyl-substituted steroids toward the zinc chloride – acetyl chloride (Tshugaev) reagent has been investigated. Maximum absorption values of reaction products were determined spectrophotometrically. A general parallelism between the Liebermann–Burchard (sulphuric acid-acetic anhydride) and the Tshugaev reagent was confirmed except in the case of 5: 6 unsaturated 7-ketosteroids, which reacted to the latter reagent only. Arguments against currently suggested mechanisms for the Liebermann–Burchard reaction are presented, and a new mechanism for color production is postulated which involves ring cleavage. Experimental support is offered.

Color Reactions of Rubber and Gutta-Percha

1929 ◽  
Vol 2 (2) ◽  
pp. 193-196
Author(s):  
F. Kirchhof
Keyword(s):  
Acetic Acid ◽  
Acetic Anhydride ◽  
Zinc Chloride ◽  
Trichloroacetic Acid ◽  
Acetyl Chloride ◽  
Oxidation Products ◽  
Arsenic Trichloride ◽  
Gutta Percha ◽  
Long Time ◽  
Color Reactions

Abstract THE present paper was suggested by a recent publication of Pauly on the same subject, who applied the well known sterol reactions of Hesse, Liebermann, Tschugajeff, etc., to the hydrocarbons of rubber and gutta-percha. These reactions depend either upon the action of concentrated H2SO4 on chloroform solutions of the substances in the presence or absence of acetic anhydride (Liebermann, Burchard and Hesse reactions) or other solvents, or condensation reagents are used, such as acetyl chloride and zinc chloride by Tschugajeff, and acetic acid with arsenic trichloride by Kahlenberg, and trichloroacetic acid with a trace of formaldehyde by Godoletz. All the known sterol reactions take place also with rubber or gutta-percha, with the appearance of intense red or violet colorations of varying stability, the color depending in part upon the quality and in part upon the purity of the samples. The Burchard reaction in particular is very sensitive in these respects. Thus with rubber purified with alkali by the Pummerer method, the color is a Bordeaux red which does not change for a long time, whereas solutions of unpurified rubber change rapidly, a change which is rightly ascribed by Pauly to relatively rapid oxidation in the presence of oxidation products in the case of the unpurified rubber.

CATALYZED NITRATION OF AMINES: VIII. THE MEDIUM USED IN NITRATION OF SECONDARY ALIPHATIC AMINES

1948 ◽  
Vol 26b (3) ◽  
pp. 294-308 ◽  
Author(s):  
Thelma Connor ◽  
George F Wright ◽  
G. N. R. Smart
Keyword(s):  
Nitric Acid ◽  
Acetic Anhydride ◽  
Hydrogen Chloride ◽  
Zinc Chloride ◽  
Acetyl Chloride ◽  
Maximum Amount ◽  
Initial Formation ◽  
Reaction Systems ◽  
Elemental Chlorine ◽  
Rate Controlling Step

The reaction [Formula: see text] has been found to be reversible in acetic anhydride. Analysis for electropositive chlorine and for nitric acid in this reacting system indicates that consumption of NO3− and production of Cl+ passes through a maximum after which nitric acid is regenerated and electropositive chlorine disappears. This phenomenon has been interpreted as an initial formation of chlorine acetate (or other chlorine ester) which then decomposes to give elemental chlorine. The increased demand for hydrogen chloride then shifts the equilibrium toward regeneration of nitric acid. The reaction has been found to be second order in its kinetics, with an activation energy of about 8000 cal. It is probably not the rate-controlling step in the catalyzed nitration, except perhaps where such nitration is easy and efficient. When nitration is difficult the electropositive chlorine tends to accumulate. When it becomes elemental chlorine, it is ineffective for nitration catalysis and is destructive to the amine. The catalysts acetyl chloride and zinc chloride have been studied. Electropositive chlorine formation occurs at the same rate with acetyl chloride as with hydrogen chloride. Zinc chloride, on the other hand, has been found to generate the maximum amount of electropositive chlorine immediately. This indicates that zinc chloride would be a good catalyst for easily nitrated amines but less efficient for amines which react more slowly, since the chlorine acetate not consumed by chloramination would decompose to give the destructive elemental chlorine. No mono-, di-, or trichloroacetic acids, nor perchloric acid, could be detected in aged reaction systems initially hydrogen chloride – nitric acid – acetic anhydride.

Photochemical reactions of azo compounds. VII. Studies of the photochemical reactions of azobenzene under various acidic conditions

1966 ◽  
Vol 19 (8) ◽  
pp. 1445 ◽  
Author(s):  
GE Lewis ◽  
RJ Mayfield
Keyword(s):  
Acetic Acid ◽  
Acetic Anhydride ◽  
Sulphuric Acid ◽  
Photochemical Reaction ◽  
Acetyl Chloride ◽  
Photochemical Reactions ◽  
Aluminium Chloride ◽  
Azo Compounds ◽  
High Yield ◽  
Acidic Conditions

An investigation has been made of the photochemical and dark reactions of azobenzene in acetic acid-ferric chloride and acetic acid-aluminium chloride mixtures for comparison with the corresponding reactions of azobenzene in sulphuric acid. The photochemical reactions resulted in cyclodehydrogenation of azobenzene to benzo[c]cinnoline, and small quantities of reduction products of azobenzene were also isolated. The formation of reduction products was again observed in the dark reactions, but there was no sign of cyclodehydrogenation. The significance of these observations is now discussed. Irradiation of azobenzene in acetyl chloride, or in acetic anhydride containing hydrogen chloride, resulted in a novel photochemical reaction in which NN?-diacetyl-4-chlorohydrazobenzene was formed in high yield.

Acetylation and Formylation of 3-Ferrocenylpyrroles

1999 ◽  
Vol 64 (1) ◽  
pp. 99-106
Author(s):  
Battsengel Gotov ◽  
Štefan Toma ◽  
Eva Solčániová
Keyword(s):  
Acetic Acid ◽  
Acetic Anhydride ◽  
Aluminum Chloride ◽  
Acetyl Chloride ◽  
Trifluoroacetic Anhydride ◽  
Acid Mixture ◽  
Chloride Method

Acetylations of 3-ferrocenyl-1-methylpyrrole as well as 3-cyano-4-ferrocenylpyrrole and 3-cyano-4-ferrocenyl-1-methylpyrrole were performed. The course of the acylation is highly dependent on the acylation agent, that is acetyl chloride/aluminum chloride (method A), trifluoroacetic anhydride-acetic acid mixture (method B) or acetic anhydride/Sc(OTf)3 (method C). Method A gives the acetylation on ferrocene moiety, method B affords the trifluoroacetylation on pyrrole moiety and method C affords pyrrole moiety acetylation. Vielsmeier-Haack formylation gives the products of substitution on pyrrole moiety.

Fast and automated identification of reactions with low barriers: the decomposition of 3-hydroperoxypropanal

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Mads Koerstz ◽  
Maria H. Rasmussen ◽  
Jan H. Jensen
Keyword(s):  
Reaction Mechanism ◽  
Systematic Approach ◽  
Transition States ◽  
Semiempirical Methods ◽  
Reaction Products ◽  
Reaction Energy ◽  
Automated Identification ◽  
Reaction Discovery ◽  
Systematic Enumeration ◽  
Computational Resources

We show how fast semiempirical QM methods can be used to significantly decrease the computational expense for automated reaction mechanism discovery, using two different method for generating reaction products: graph-based systematic enumeration of all possible products and the meta-dynamics approach by Grimme (J. Chem. Theory. Comput. 2019, 15, 2847). We test the two approaches on the low-barrier reactions of 3-hydroperoxypropanal, which have been studied by a large variety of reaction discovery approaches and therefore provides a good benchmark. By using PM3 and GFN2-xTB for reaction energy and barrier screening the systematic approach identifies 64 reactions (out of 27,577 possible reactions) for DFT refinement, which in turn identifies the three reactions with lowest barriers plus a previously undiscovered reaction. With optimized hyperparameters meta-dynamics followed by PM3/GFN2-xTB-based screening identifies 15 reactions for DFT refinement, which in turn identifies the three reactions with lowest barrier. The number of DFT refinements can be further reduced to as little as six for both approaches by first verifying the transition states with GFN1-xTB. The main conclusion is that the semiempirical methods are accurate and fast enough to automatically identify promising candidates for DFT refinement for the low barrier reactions of 3-hydroperoxypropanal in about 15-30 minutes using relatively modest computational resources.

Product distributions and isotopic selectivities in ir multiphoton dissociation of pentafluoroiodoethane

1981 ◽  
Vol 59 (9) ◽  
pp. 1307-1310 ◽  
Author(s):  
E. Weinberg ◽  
M. Gauthier ◽  
P. A. Hackett ◽  
C. Willis
Keyword(s):  
Reaction Mechanism ◽  
Bond Cleavage ◽  
Thermal Dissociation ◽  
Infrared Multiphoton Dissociation ◽  
High Fluence ◽  
Reaction Products ◽  
Product Distributions ◽  
Multiphoton Dissociation

Infrared multiphoton dissociation of pentafluoroiodoethane leads to a complex array of reaction products. For photolysis in the v4 band the reaction mechanism involves C2F5—I bond cleavage followed by thermal dissociation of C2F5 radicals. For irradiation within the v3 band at high fluence, efficient secondary photolysis of C2F5 radicals is postulated. At lower fluences the dissociation is isotopically selective leading to C4F10 enriched in carbon-13.

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