Dibromomethane Research Articles

The resilience of chemically modified cottons. I. Reactions of alkali cellulose and of sodium cellulosates with methylene dibromide

AbstractA study has been made of the reactions of alkali cellulose with methylene dihalides, particularly methylene dibromide. These reactions have involved cotton cellulose in a swollen state, and the treated fabrics have been found to exhibit improved wet crease recovery, with little or no effect on dry crease recovery. The rates of reaction of methylene dibromide with alkali celluloses prepared from potassium hydroxide have been found to be more than double those with alkali cellulosed prepared from sodium hydroxide. The energies of activation in both cases are about 25 kcal./mole, statistically indistinguishable for the two types of alkali, and consistent with the view that covalent bonds are being formed in the course of reaction. The implications and limitations of these results are discussed. Studies have also been made of the reactions of sodium cellulosates with methylene dibromide. In one case, the sodium cellulosates were prepared by reaction of the cellulose with sodium dissolved in liquid ammonia. Here, the reactions appear interesting, but essentially difficult to control. Sodium cellulosates were also prepared by reaction of the cellulose with sodium isoamylate in xylene. When proper care is taken to exclude water from the reaction system, it is found that the reproducibility of duplicate experiments is quite good and that the rate of reaction of the sodium cellulosate with methylene dibromide is much greater than that found for an alkali cellulose prepared from sodium hydroxide.

The use of methyl iodide-propane mixtures and tri-fluoro bromo methane as bubble chamber fluids

The suitability of a methyl iodide-propane system as a «heavy liquid» bubble chamber medium has been investigated. Operating conditions have been found for various mixtures, and also for tri-fluoro bromo methane, another possible heavy liquid medium.

On the Reaction between Substituted Malonic Esters and Methylene Bromide. II.

On the Reaction between Substituted Malonic Esters and Methylene Bromide. II.

On the Reaction between Substituted Malonic Esters and Methylene Bromide. I.

On the Reaction between Substituted Malonic Esters and Methylene Bromide. I.

On the Reaction between Substituted Cyanoacetic Esters and Methylene Bromide. The Preparation of alpha,alpha'-Di-(tert.-butyl)-glutaric Acid.

On the Reaction between Substituted Cyanoacetic Esters and Methylene Bromide. The Preparation of alpha,alpha'-Di-(tert.-butyl)-glutaric Acid.

The heat capacities of certain liquids

The heat capacities and adiabatic compressibilities of carbon tetrachloride, chloroform, methylene dibromide and m ethyl iodide have been measured between about — 30 and 30° C. The heat capacities at constant volume have been derived, and it is emphasized th a t these quantities apply to particular volumes existing at different temperatures. An isotherm for liquids, based on high-pressure data, has been used to obtain an expression for the effect of change of volume on the heat capacity at constant volume. This relation has been applied to mercury, carbon disulphide, carbon tetrachloride, chloroform and water. Satisfactory agreement has been obtained with the results found in other ways by Bridgman (1911, 1912) on mercury and water and by Gibson & Loeffler (1941) on carbon tetrachloride and water. From the results found in this work on the resolution of the various energy contributions to the liquid heat capacities of polyatomic molecules other than water, it is concluded that the concept of molecular rotation about a preferred axis can explain most of the facts established. There remains, however, a structural contribution to the total heat capacity which is approximatelyRcal mole-1deg.-1.

Viscosities of Fluorinated Methyl Bromides and Chlorides.

I n s tudying t h e chemica l reac t ions of t h e f luorinated methyl ch lor ides and bromides with sodium vapor, i t w a s n e c e s s a r y t o obta in t h e v i s c o s i t i e s of t h e s e ha l ides . Very few d a t a on t h e v i s c o s i t i e s of t h e s e compounds a r e recorded; t h e v a l u e s that e x i s t h a v e been obtained by independent measurements and provide no opportunity for internal comparison or cons is tency .

“Infrared Spectra of Steroids. II. The Influence of the Solvent on Carbonyl Frequency Correlations”

The influence of solvents on frequencies of the carbonyl absorption bands in the infrared spectra of 56 steroids has been investigated with a double beam spectrophotometer. Good agreement was obtained with data previously published for the characteristic frequencies in carbon disulfide for similar types of ketosteroids. The carbonyl absorption maxima in chloroform and methylene bromide were displaced toward lower frequencies by about 2–17 cm−1 from their frequencies in carbon disulfide or carbon tetrachloride. The magnitude of the shift depended upon the location and type of carbonyl group. Additional dispalcement of the order of 1–19 cm−1 was found in bromoform solution. In mineral oil spectra, considerable variation in frequencies were observed for a particular carbonyl group at the same position in different steroid molecules. The absorption maxima of two Δ5-7-ketosteroids are reported for the first time to be at the same position as those of Δ4-3-ketosteroids. A new interaction of the 3 a, 9a-epoxides with the 11 carbonyl group has been suggested. While Δ4-3-ketosteroids could not be distinguished from Δ9-12-ketosteroids in carbon disulfide or carbon tetrachloride, the absorption maxima were at sufficiently different frequencies in chloroform or methylene bromide. In a series of four ketones with the carbonyl group at different positions along the side chain, it was observed that the 24 and 25 carbonyl absorption bands were closer to those of simple aliphatic ketones than the 20 and 22 ketones. A similar shift to higher frequencies as the chain length was increased was observed for three steroid acids. When the ketonic absorption band was very close to that of an acetate, broadening of the latter band in chloroform, methylene bromide and bromoform resulted in poor resolution.

THE PHOTOLYSIS OF MIXTURES OF ACETONE AND SOME HALOGENATED HYDROCARBONS

The composition of the products of photolysis of acetone in the presence of methyl chloride, methyl bromide, methylene chloride, and methylene bromide has been determined. These reactions are attended by complications not found with the photolysis of acetone–hydrocarbon mixtures. Failure to take into account reactions resulting from the formation of halogen hydrides and to allow for the presence of ethylene invalidates the values obtained by Raal and Steacie for the activation energy for hydrogen abstraction by methyl radicals from some halogenated hydrocarbons.

Fine structure in some infrared bands of methylene halides

The infrared absorption spectra of methylene chloride, methylene bromochloride, and methylene bromide have been studied with a high-resolution grating spectrometer in the region from 1.6 to 2.3 microns. The purpose of these measurements was to determine the molecular constants of these molecules from their spectra. Using the saturated vapor in a cell 60 centimeters long, it was possible to resolve the fine structure in three to five bands of each molecule. All the resolved bands are overtones and combinations of fundamental vibrations localized in the methylene radical, and hence appear at nearly the same frequencies for each molecule. Bands with Q branches (symmetry types B and C) and without that feature appear. Application of combination relations to all bands of a given molecule yield rotational spacings of the ground state agreeing within 0.5 percent. The spacings, [A — (B + C)I2\, are, respectively, for CH2C12, 0.955 cm ; CH2BrCl, 0.898 cm ; and CH2Br2, 0.821 cm. The molecular dimensions cannot be uniquely determined from these data alone, but if tetrahedral angles are assumed, they lead to improbably low values of the C — halogen distance, namely, 1.70 A for C —Cl and 1.83 A for C — Br. If the halogen — C — halogen angle is increased to 112°, as found by electron diffraction, the C — Cl distance is in good agreement with the electron diffraction distance 1.766 A, and C —Br becomes 1.907 A in CH2Br2 and 1.911 in CH2BrCl.

The Reaction of Methyl Radicals with Some Halogenated Methanes

The reactions of methyl radicals formed by the photolysis of acetone with several halogenated methanes have been investigated between 110°C and 220°C. The activation energies of these reactions have been determined relative to the activation energy of the combination of methyl radicals and are found to be (in kcal): methyl fluoride 8.7, methylene fluoride 6.2, methyl chloride 9.4, methylene chloride 7.2, chloroform 5.8, methyl bromide 10.1, methylene bromide 8.7. The steric factors of the reactions are in the range 10−2−10−4.

Kinetics of the Reactions of Thiosulfate Ion with Methyl and Isobutyl Bromides

Kinetics of the Reactions of Thiosulfate Ion with Methyl and Isobutyl Bromides

Methylene Bromide as a Quenching Agent in Geiger–Müller Counters

GEIGER-MULLER counters filled with methylene bromide and argon are known1 to be self-quenching and to possess long sloping plateaux. Measurements have now been made of the β-counting-rate as a collimated source was moved diametrically across the mica end-window of a β-ray counter so that β-particles entered the counter parallel to the centre wire. Two counters A and B of identical construction were used for these measurements, A containing argon at a pressure of 97 mm. of mercury and ethyl alcohol at a pressure of 9·7 mm. of mercury, and B containing argon at a pressure of 7·4 mm. of mercury and methylene bromide at a pressure of 7·4 mm. of mercury. It was found that the efficiency of counter B was greatest for particles entering the counter near the centre wire, but even then was less than that of counter A by a factor of about three.

The Discharge Mechanism of Self-Quenching Geiger-Mueller Counters

A split counter arrangement was used to investigate the absorption coefficient of the radiation which causes the discharge to spread along the wire of a counter after the triggering of a pulse. The counters used were filled with methylene bromide and argon at various pressures, and with ethyl alcohol and argon. The results indicate that the vapor dissipates electron energies, thereby reducing the number of photons produced during the discharge. It was also observed that the absorption coefficient is a function of the argon alone, from which it was concluded that photo-ionization of the argon is responsible for spreading the discharge along the wire. This behavior was also observed with helium and neon in combination with alcohol or methylene bromide.

46. Mechanism of substitution at a saturated carbon atom. Part XXVIII. The rôle of steric hindrance. (Section C) a comparison of the rates of reaction of methyl, ethyl, n-propyl, isobutyl, and neopentyl bromides with aqueous ethyl alcohol

46. Mechanism of substitution at a saturated carbon atom. Part XXVIII. The rôle of steric hindrance. (Section C) a comparison of the rates of reaction of methyl, ethyl, n-propyl, isobutyl, and neopentyl bromides with aqueous ethyl alcohol

44. Mechanism of substitution at a saturated carbon atom. Part XXVI. The rôle of steric hindrance. (Section A) introductory remarks, and a kinetic study of the reactions of methyl, ethyl, n-propyl, isobutyl, and neopentyl bromides with sodium ethoxide in dry ethyl alcohol

The first page of this article is displayed as the abstract.

49. Mechanism of substitution at a saturated carbon atom. Part XXXI. The rôle of steric hindrance. (Section F) a comparison of the rates of reaction of methyl, ethyl, n-propyl, and neopentyl bromides with wet formic acid

The first page of this article is displayed as the abstract.

Raman Spectra of Compounds in the Gaseous and Liquid States

An apparatus for exciting the Raman spectra of gases and liquids at temperatures up to 300°C is described. For phosphorus trichloride, methyl chloride, methyl bromide, methyl alcohol, methylene chloride, methylene bromide, chloroform, and carbon tetrachloride, the Raman spectra of the gas and the liquid at the same temperature have been photographed in juxtaposition with a liquid-prism spectrograph of speed f: 2.9 and linear dispersion 27A/mm at 4400A. The Raman spectra of gaseous n-pentane, n-hexane, and deuterium oxide have been photographed with 2537A excitation. The change in the Raman frequencies with the state of aggregation is different for different vibrations and varies greatly from compound to compound. In the absence of an adequate theory for this phenomenon, a search has been made for empirical regularities. The perpendicular bands of the symmetrical-top molecules are much less diffuse in the liquid than in the gas, showing that the intermolecular forces are effective in quenching the rotation of the molecules in the liquid. The other bands are about equally sharp in gas and liquid.

The Determination of the Structures of Methane Derivatives by the Electron Diffraction Method

The molecular structures of several bromine and iodine derivatives of methane have been determined by the electron diffraction method. For tertiary butyl bromide it has been found that the tertiary carbon atom has the tetrahedral angles between the valence bonds, and the interatomic distances are: tertiary C— methyl C 1.55A and tertiary C–Br 2.06A. In methyl bromide and iodide the C—X distances are 2.06 and 2.28A, respectively. In methylene bromide and iodide it has been found that the angle between the C—X bonds is 125° and the interatomic distances are: C–Br 2.03, Br–Br 3.61, C–I 2.28 and I–I 4.06A. In bromoform the angles formed by the C–Br bonds are 115°, and the interatomic distances are: C–Br 2.05 and Br–Br 3.46A.

The refraction and dispersion of some gaseous compounds

In the present paper, results are given of measurements which have been made by the author on the refraction and dispersion of the following substances in the gaseous state :— (1) Silicon tetrachloride, SiCl 4 ; (2) silicon tetrabromide, SiBr 4 ; (3) boron trichloride, BCl 3 ; (4) boron tribromide, BBr 3 ; (5) phosgene, COCl 2 ; (6) acetone, (CH 3 ) 2 CO; (7) ethyl ether, (C 2 H 5 ) 2 O; (8) acetylene, C 2 H 2 ; (9) ethylene, C 2 H 4 ; (10) ethane, C 2 H 6 ; (11) methyl chloride, CH 3 Cl; (12) methylene chloride, CH 2 Cl 2 ; (13) methylene bromide, CH 2 Br 2 . The gaseous refractivities of six of these compounds (viz., silicon tetrachloride, silicon tetrabromide, boron trichloride, boron tribromide, methylene chloride, methylene bromide) have not been previously determined and the recorded data for the remaining substances are either so meagre or discordant that further determinations were obviously called for.