Studies of the Wallach Transformation. II. Steric Effects in Some Symmetrically Disubstituted Azoxybenzenes

1951 ◽  
Vol 4 (2) ◽  
pp. 185
Author(s):  
PH Gore ◽  
GK Hughes
Keyword(s):  
Sulphuric Acid ◽  
Important Influence ◽  
Steric Effects ◽  
Hydroxyl Group ◽  
Azoxy Compounds ◽  
Point Of Entry ◽  
Substituent Group

Study of the behaviour of symmetrical azoxy compounds in the Wallach Transformation shows the important influence of size of a substituent group ortho to the point of entry of the hydroxyl group.�The various processes known to occur in a solution of azoxybenzene in sulphuric acid are discussed.

Study of naphthopyran derivatives: structure and photochromic properties in solution and in polymer film

2021 ◽  
Vol 77 (7) ◽  
Author(s):  
Linqi Shi ◽  
Zipei Sun ◽  
Jiajie Tian ◽  
Yaodong Huang ◽  
Jiben Meng
Keyword(s):  
Uv Light ◽  
Steric Effects ◽  
Pmma Film ◽  
Structure Property ◽  
Photochromic Properties ◽  
X Ray ◽  
Structure Property Relationships ◽  
Substituent Group ◽  
Uv Light Irradiation ◽  
Electronic And Steric Effects

Four naphthopyran derivatives, namely, 3,3-bis(naphthalen-1-yl)-3H-naphtho[2,1-b]pyran, C33H22O, NP1, 3,3-bis([1,1′-biphenyl]-4-yl)-3H-naphtho[2,1-b]pyran, C37H26O, NP2, 3,3-bis(4-phenoxyphenyl)-3H-naphtho[2,1-b]pyran, C37H26O2, NP3, and 3,3-bis(4-methoxy-2-methylphenyl)-3H-naphtho[2,1-b]pyran, C29H26O3, NP4, were synthesized and their photochromic properties investigated. NP1–NP4 exhibited good photochromism in different solutions and in poly(methyl methacrylate) (PMMA) film under UV light irradiation. Solvatochromism and the electronic and steric effects of the substituent group on photochromism were analyzed and decolouration curves were found to fit a monoexponential kinetic decay in most cases. Single-crystal X-ray analysis of NP1 and NP2 revealed the structure–property relationships. Good fatigue resistance of NP1, both in solution and in the PMMA film, endows it with potential value for applications.

THE ABSORPTION AND FLUORESCENCE PROPERTIES, IN THE VISIBLE SPECTRAL REGION, OF CERTAIN STEROIDS IN SULPHURIC ACID SOLUTIONS

1952 ◽  
Vol 30 (3) ◽  
pp. 213-230
Author(s):  
J. H. Linford ◽  
O. Bernice Paulson
Keyword(s):  
Acid Solution ◽  
Sulphuric Acid ◽  
Testosterone Propionate ◽  
Sulphuric Acid Solution ◽  
Visible Spectral Region ◽  
Hydroxyl Group ◽  
Acid Solutions ◽  
Steroid Molecule ◽  
Desoxycorticosterone Acetate ◽  
Colored Compound

The absorption and fluorescence of steroids dissolved in concentrated sulphuric acid, and the changes in these properties on adding ethanol to the concentrated acid solutions, have been examined for: cholesterol, pregnandiol, α-estradiol, dehydroisoandrosterone (D.H.A.), dehydroisoandrosterone acetate, desoxycorticosterone acetate, (D.O.C.A.), testosterone propionate, and progesterone. At 57° C. or less, in concentrated sulphuric acid solution a colored compound was formed only if an hydroxyl group was present in the steroid molecule; the keto group formed a colored compound with sulphuric acid only in the presence of a hydroxyl group in the same steroid molecule. As the concentrated sulphuric acid solutions were diluted with alcohol, absorption maxima appeared which were characteristic of specific hydroxyl and keto groups. Irradiation of the solutions by light of the spectral regions corresponding to the absorption maxima produced related fluorescent bands.

EXPERIMENTS ON THE USE OF SILICIC ACID FOR STEROID CHROMATOGRAPHY

1956 ◽  
Vol 34 (1) ◽  
pp. 1153-1168 ◽  
Author(s):  
J. H. Linford
Keyword(s):  
Sulphuric Acid ◽  
Silicic Acid ◽  
Silica Surface ◽  
Solid Phase ◽  
Free Water ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Color Reagent

Mixtures of pure sterols, and extracts of hydrolyzed urine, were chromatographed on columns of silicic acid. The results were observed spectrometrically using a sulphuric acid – methanol color reagent. Dry silicic acid retained or altered the sterols. When the silicic acid contained free water the sterols were distributed between the surface of the solid and the developing solvent. The adherence to the solid phase decreased with increase of free water and with increased solubility of the sterol in the solvent. As the free water was increased liquid–liquid partition was observed. The adherence of the sterol to the silica surface increased with the number of hydroxyl groups in the sterol molecule. Silicic acid columns are therefore particularly suited to the separation of sterols that differ in their number of hydroxyl groups and to the detection of the production of artifacts by loss of the hydroxyl group.

PROTONATION OF THE CARBONYL GROUP: II. THE BASICITIES OF SUBSTITUTED BENZALDEHYDES

1959 ◽  
Vol 37 (4) ◽  
pp. 664-671 ◽  
Author(s):  
K. Yates ◽  
Ross Stewart
Keyword(s):  
Sulphuric Acid ◽  
Carbonyl Group ◽  
Spectrophotometric Method ◽  
Ultraviolet Absorption ◽  
Steric Effects ◽  
Acid Media ◽  
Substituted Benzaldehydes ◽  
Group Ii

The basicities of seven meta- and para-substituted benzaldehydes have been determined by a spectrophotometric method in sulphuric acid media. The simple Hammett relation does not hold for these bases but a good correlation exists between [Formula: see text] and σ+. The effects of substitution on the wavelengths of maximal ultraviolet absorption in benzaldehyde are compared with those in acetophenone.The basicity of o-tolualdehyde was determined in an attempt to estimate the steric effects of ortho substitution. The effects of symmetrical trisubstitution on the basicity of benzaldehyde and acetophenone are compared and discussed.

THE IDENTIFICATION OF AZOXY COMPOUNDS

1949 ◽  
Vol 27b (12) ◽  
pp. 897-901 ◽  
Author(s):  
Roger Gaudry ◽  
Karl F. Keirstead
Keyword(s):  
Sulphuric Acid ◽  
Zinc Dust ◽  
Para Isomer ◽  
Azo Compound ◽  
Azoxy Compounds ◽  
Azoxy Compound ◽  
First Time

An azoxy compound can be treated with concentrated sulphuric acid to produce a nydroxyazo product consisting chiefly of the para isomer. This reaction, the Wallach rearrangement, is the basis for a suggested generic test for an azoxy compound. For the identification of a given azoxy compound, two derivatives are suggested: the hydrazo compound produced by the reduction of the azoxy compound by zinc dust, and the azo compound produced by the oxidation of the hydrazo compound. These compounds are described for the first time: 2,2′-dichloro-4-hydroxyazobenzene, 2,5′,2,5′-tetrachloro-4-hydroxyazobenzene, 2,2′-dimethoxy-5,5′-dichloroazobenzene, 3,3′,4,4′-tetrachlorohydrazobenzene, 2,2′-dimethyl-3,3′-dichlorohydrazobenzene, and 2,2′-dimethoxy-5,5′-dichlorohydrazo-benzene.

Fragmentation of tertiary alkyl carbonium ions in sulphuric acid : steric effects.

1971 ◽  
Vol 12 (18) ◽  
pp. 1349-1350 ◽  
Author(s):  
J.E. Dubois ◽  
J.S. Lomas ◽  
D.S. Sagatys
Keyword(s):  
Sulphuric Acid ◽  
Steric Effects ◽  
Carbonium Ions ◽  
Tertiary Alkyl

A Study of Steric Effects on Nitromethylene Acidity and the Mechanism of Epimerization in Partially Blocked Nitro Hexoses

1971 ◽  
Vol 49 (19) ◽  
pp. 3197-3202 ◽  
Author(s):  
Hans H. Baer ◽  
Werner Rank
Keyword(s):  
Potassium Hydroxide ◽  
Potassium Hydroxide Solution ◽  
Alcoholic Solution ◽  
Steric Effects ◽  
Hydroxyl Group ◽  
Henry Reaction ◽  
Hydroxide Solution

The extent of nitronate formation in seven methyl 4,6-O-benzylidene-3-deoxy-3-nitrohexopyranosides and four methyl 4,6-O-benzylidene-2,3-dideoxy-3-nitrohexopyranosides in dilute potassium hydroxide solution was compared by means of u.v. spectroscopy. Considerable differences were found to exist in the nitromethylene acidities, and these were correlated with stereochemical features of the molecules. A facile manno → gluco epimerization occurring in this series was investigated. It was shown that, in alkaline alcoholic solution, the epimerization proceeds by an elimination–addition via an intermediate nitroalkene if the hydroxyl group at C-2 is acetylated. However, if the hydroxyl is free, the nitroalkene is not an intermediate and, in accord with the low nitromethylene acidity in this particular case, the mechanism is suggested to involve a reverse Henry reaction.

Déshydratation des diols-1,2 α,β-éthyléniques IV: rôle de la stéréomutation des carbocations allyliques α-hydroxylés sur l'orientation des réactions observées

1980 ◽  
Vol 58 (14) ◽  
pp. 1451-1462 ◽  
Author(s):  
Gilbert Dana ◽  
Josyane Gharbi-Benarous ◽  
Sa Le Thi Thuan
Keyword(s):  
Type A ◽  
Steric Effects ◽  
Hydroxyl Group ◽  
Degradation Reaction

The allylic carbocations[Formula: see text]formed during the dehydration of diols of type A[Formula: see text]are found to react by five different processes: three nucleophilic attacks (by solvent at the β or δ positions, or by the intramolecular hydroxyl group at δ), a degradation reaction between Cα, and Cβ and the classical pinacol rearrangement.Nucleophilic attack at the carbon δ is a very efficient reaction and sometimes (for monosubstituted substrates in β, γ or δ) gives quasi-exclusive products: a ketone for the reaction with H2O in δ or a 2,5-dihydrofuran product for the intramolecular reaction.In the case of γ and δ disubstituted carbocations, the selectivity is less and we show that it is possible to analyze the different steric effects commanding the stereomutation equilibrium of the allylic carbocation and so determining the orientation in the dehydration.

EXPERIMENTS ON THE USE OF SILICIC ACID FOR STEROID CHROMATOGRAPHY

1956 ◽  
Vol 34 (6) ◽  
pp. 1153-1168 ◽  
Author(s):  
J. H. Linford
Keyword(s):  
Sulphuric Acid ◽  
Silicic Acid ◽  
Silica Surface ◽  
Solid Phase ◽  
Free Water ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Color Reagent

Mixtures of pure sterols, and extracts of hydrolyzed urine, were chromatographed on columns of silicic acid. The results were observed spectrometrically using a sulphuric acid – methanol color reagent. Dry silicic acid retained or altered the sterols. When the silicic acid contained free water the sterols were distributed between the surface of the solid and the developing solvent. The adherence to the solid phase decreased with increase of free water and with increased solubility of the sterol in the solvent. As the free water was increased liquid–liquid partition was observed. The adherence of the sterol to the silica surface increased with the number of hydroxyl groups in the sterol molecule. Silicic acid columns are therefore particularly suited to the separation of sterols that differ in their number of hydroxyl groups and to the detection of the production of artifacts by loss of the hydroxyl group.

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