Contrast agents halides

In contrast, if halide-based ionic liquids were used under similar conditions, halogenated products were isolated. If hydrochloric acid was used in a nitrate-based ionic liquid, halogenated products also resulted. In methanesulfonate-based ionic liquids, nitric acid acts as an oxidising agent rather than a nitrating agent, which is capable of oxidising toluene to benzoic acid. Likewise it was possible to use a nitrate-based ionic liquid with added methanesulfonic acid [127],... 

In the early days of organic chemistry, alkenes were described as unsaturated because, in contrast to the saturated alkanes, they were found to react readily with substances such as halogens, hydrogen halides, oxidizing agents, and so on. Therefore, the chemical affinity of alkenes was regarded as unsatisfied or unsaturated. (Also see Section 1-11.)... 

Increasing the amount of accelerator in a developer will increase the contrast. This is because it creates a more active environment in which the developing agent can reduce additional silver halide in the exposed areas. However, too much accelerator will increase fog levels, necessitating the addition of bromide or some other form of restrainer. While paper developers should always contain some restrainer, when formulating a film developer it is better to decrease the accelerator rather than add more restrainer. 

In contrast to these alkylaluminum catalyst systems, the well-known Friedel-Crafts halides—e.g., A1C13, AlEtCl2, etc.—rapidly polymerize isobutylene to high molecular weight products in the absence of added cocatalyst. It is usually presumed, but remains to be proved, that traces of moisture or HC1 provide the necessary cocatalyst with the latter agents. 

In contrast to esterification, etherification is carried out in an alkaline medium and the etherifying agents are alkyl halides. The general reaction is termed aliphatic nucleophilic substitution and, employed under normal conditions, is of the bimolecular type. 

The yields are lower because of competing hydrolysis during the aqueous work-up. Lithioynamines 44 must be used with unreactive halides such as carbamoyl chlorides and imidoyl halides (93) The scope of this reaction seems to be limited only by the availability of the requisite acyl chlorides. It is less surprising, therefore, that a single paper reports the preparation of about sixty push-pull acetylenes In contrast, silylated ynamines, react only with very strong acylation agents, e.g. trichloroacetyl and nitrobenzoyl chloride as well as with phosgeniminium chloride. 

Alkynylmagnesium halides are less basic than the alkali metal acetylides and therefore can be applied to sensitive alkylating agents. In contrast to the alkali metal acetylides they do not react with saturated primary halides. On the other hand, they do react with allylic, propargylic and benzylic halides, but only in the presence of cuprous chloride catalysts. They also react with a-haloethers (e.g. equation 136)" . 

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