Acids, organic halogen-atom substituted

Organosulfur Halides. When sulfur is directly linked only to an organic radical and to a halogen atom, the radical name is attached to the word sulfur and the name(s) and number of the halide(s) are stated as a separate word. Alternatively, the name can be formed from R—SOH, a sulfenic acid whose radical prefix is sulfenyl-. For example, CH3CH2—S — Br would be named either ethylsulfur monobromide or ethanesulfenyl bromide. When another principal group is present, a composite prefix is formed from the number and substitutive name(s) of the halogen atoms in front of the syllable thio. For example, BrS—COOH is (bromothio)formic acid. 

The replacement of an alcoholic hydroxyl group by a halogen atom is one of the most common reactions carried out in organic chemistry. The usual reagents for effecting the transformation include halogen acids, thionyl chloride, and phosphorus halides. The reaction is of particular theoretical interest since experiments with optically active alcohols suggest still another substitution process. It has been called an internal nucleophilic substitution reaction (S i).20... 

Nucleophilic substitution of halogen atoms in highly electrophilic arenes (most often nitroarenes) by carbanions proceeds efficiently under PTC conditions. However, the catalytic process operates only with methynic carbanions, when the products do not possess an acidic hydrogen atom. In the case of methylenic carbanions, introduction of nitroaryl substituents gives products that are much stronger C-H acids thus, they are immediately converted into nitrobenzylic carbanions which, associated with the lipophilic TAA cations of the catalyst, stay in the organic phase. The low nucleophilic activity of these carbanions prevents their further reactions. In this situation the catalytic process is arrested. 

Summary Mixed functionalized octa( -alkyl/halogenalkylsilsesquioxanes) with different side chains has been prepared by acid-catalyzed cohydrolysis of w-alkyl- and lialogenalkyltrichlorosilanes. The silsesquioxane mixtures were separated in preparative amounts with normal-phase HPLC. Mixed functionalized octa( -alkyl/halogenalkylsil-sesquioxanes) with different side chains are suitable examples of an organically modified silica gel. They can be modified by nucleophilic substitution of the halogen atom with -PPh and rhodium-phosphino complexes are be formed. 

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