Halogenated structures

Johansson C, Pavasars I, Boren H, Grimvall A, Dahlman O, Morck R, Reimann A (1994) A Degradation Procedure for Determination of Halogenated Structural Elements in Organic Matter from Marine Sediments. Environ Int 20 103... 

Typically a brominated or chlorinated organic compound is added to the polymer or, in suitable cases, halogenated structures are introduced into the polymer chain by copolymerization to prepare fire-retardant polymer materials. Metal compounds, such as antimony trioxide, which do... 

Johansson C., Pavasars I., Boren H., and Grimvall A. (1994) A degradation procedure for determination of halogenated structural elements in organic matter from marine sediments. 

Halogenated natural products are mainly known from marine organisms, fungi and higher plants. The halogenated structures isolated from liverworts should, of course, have chemotaxonomical significance. 

Bromotrichloromethane is expected to have low mobility in soil. The potential for volatilization of bromotrichloromethane from dry soil surfaces may exist based on a measured vapor pressure of 39 mmHg. Based upon the highly halogenated structure of bromotrichloromethane, biodegradation in soil is expected to be slow. 

Brown, C. E., Kovacic, R, Wilkie, C. A., Hein, R. E., Yaniger, S. I., and Cody, R. B. J., "Polynuclear and Halogenated Structures in Polyphenylenes Synthesized from Benzene, Biphenyl, and p-Terphenyl under Various Conditions Characterization by Laser Desorption/Fourier Transform Mass Spectrometry,". Polym. Sci. Polym. Chem, Ed, 24, 255-267,1986. 

According to the NMR spectroscopy, polymer molecules with di-halogen structural units (Scheme 6) and their statistic distribution in the macro chain serve as the main products of syndiotactic 1,2-PB halogena-tion [16, 43]. 

Ab-initio calculations are particularly usefiil for the prediction of chemical shifts of unusual species". In this context unusual species" means chemical entities that are not frequently found in the available large databases of chemical shifts, e.g., charged intermediates of reactions, radicals, and structures containing elements other than H, C, O, N, S, P, halogens, and a few common metals. 

It is frequently advisable in the routine examination of an ester, and before any derivatives are considered, to determine the saponification equivalent of the ester. In order to ensure that complete hydrolysis takes place in a comparatively short time, the quantitative saponi fication is conducted with a standardised alcoholic solution of caustic alkali—preferably potassium hydroxide since the potassium salts of organic acids are usuaUy more soluble than the sodium salts. A knowledge of the b.p. and the saponification equivalent of the unknown ester would provide the basis for a fairly accurate approximation of the size of the ester molecule. It must, however, be borne in mind that certain structures may effect the values of the equivalent thus aliphatic halo genated esters may consume alkali because of hydrolysis of part of the halogen during the determination, nitro esters may be reduced by the alkaline hydrolysis medium, etc. 

As well as the cr-complexes discussed above, aromatic molecules combine with such compounds as quinones, polynitro-aromatics and tetra-cyanoethylene to give more loosely bound structures called charge-transfer complexes. Closely related to these, but usually known as Tt-complexes, are the associations formed by aromatic compounds and halogens, hydrogen halides, silver ions and other electrophiles. 

In TT-complexes formed from aromatic compounds and halogens, the halogen is not bound to any single carbon atom but to the 7r-electron structure of the aromatic, though the precise geometry of the complexes is uncertain. The complexes with silver ions also do not have the silver associated with a particular carbon atom of the aromatic ring, as is shown by the structure of the complex from benzene and silver perchlorate. ... 

Cation (Section 1 2) Positively charged ion Cellobiose (Section 25 14) A disacchande in which two glu cose units are joined by a 3(1 4) linkage Cellobiose is oh tamed by the hydrolysis of cellulose Cellulose (Section 25 15) A polysaccharide in which thou sands of glucose units are joined by 3(1 4) linkages Center of symmetry (Section 7 3) A point in the center of a structure located so that a line drawn from it to any element of the structure when extended an equal distance in the op posite direction encounters an identical element Benzene for example has a center of symmetry Cham reaction (Section 4 17) Reaction mechanism m which a sequence of individual steps repeats itself many times usu ally because a reactive intermediate consumed m one step is regenerated m a subsequent step The halogenation of alkanes is a chain reaction proceeding via free radical intermediates... 

The most widely used method for the synthesis of thiazoles (see Chapter 4.19) is of this type and involves the reaction of a-halo compounds (Y = halogen in Scheme 2) with a reactive component containing an —C(=S)— structural entity. Reaction of the a-... 

---