Halogen hydrogenation with

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. 

Halogen exchange with KF is not successful ia acetic acid (10). Hydrogen bonding of the acid hydrogen with the fluoride ion was postulated to cause acetate substitution for the haUde however, the products of dissolved KF ia acetic acid are potassium acetate and potassium bifluoride (11). Thus KF acts as a base rather than as a fluorinating agent ia acetic acid. 

Halogens, Hydrogen Halides, and Other Covalent Halides. Most compounds containing Si—H bonds react very rapidly with the free halogens. An explosive reaction takes place when chlorine or bromine is allowed to react with SiH at room temperature, presumably forming halogenated silane derivatives (3). At lower temperatures, the reactions are moderated considerably, for example. 

Reactive halogens in various series have been removed by catalytic hydrogenation with either platinum or palladium catalysts, and other nucleophiles which have been used in chloride displacements include hydroxide ion, alkoxides, hydrosulflde, hydrazine and toluene-p-sulfonylhydrazine, and trimethyl phosphite. 

The replacement of hydrogen with halogen takes place under thermal or photochemical conditions [J9, 20, 21] (equations 10-12). 

Replacement of hydrogen with halogen in fluoraarenes takes place by an ionic mechanism and is subject to the normal directing effects [27, 28, 29] (equations 13-15). 

Replacement of hydrogen with halogen can be carried out in the alpha position of fluorinated ethers, amines, aldehydes, or nitriles In 2,2,3,4,4,4 hexafluoro-bulyl methyl ether, chlorination occurs predominantly at the methyl, however, bromination occurs mostly at the internal position of the fluorobutyl group 133] (equation 20)... 

Table 8. Replacement of Hydrogen with Halogen in Benzotrifluoride...

OL Halogenation (Sections 18.2 and 18.3) Halogens react with aldehydes and ketones by substitution an a hydrogen is replaced by a halogen. Reaction occurs by electrophilic attack of the halogen on the carbon-carbon double bond of the enol form of the aldehyde or ketone. An acid catalyst increases the rate of enolization, which is the ratedetermining step. 

C15-0125. At least three possible reaction mechanisms exist for the reaction of hydrogen with halogens, H2 + 2 2 H JT. Determine the rate law predicted by each of them ... 

Maurer and Bohme62 reported that one mole of XIV, with acid chlorides in acid solution or with dry hydrogen chloride in ether, adds on halogen acid with the simultaneous production of two moles of benzoic acid per... 

The oxidation of thioamides 63 with a wide variety of oxidizing agents is a well-employed method for the synthesis of 3,5-disubstituted-l,2,4-thiadiazoles 64 <1982AHC285>. However, this method is limited mainly to arylthioamides. The most common oxidizing agents tend to be halogens, hydrogen peroxide, dimethyl sulfoxide (DMSO), and nitrous acid. Yields from these reactions are variable and depend on the thioamide, oxidant, and conditions used (Equation 19). By-products such as nitriles and isothiocyanates are usually formed. 

None of the halogens react with water to form H2(g). In order to displace molecular hydrogen from water, one must add a strong reducing agent, such as sodium metal. 

RhX(CO)(PPh3)2 [X=halogen] complexes with hydrogen. The reaction for X=C1 is shown in Figure 11.3. 

X is always used as the general representation for any of the halogens. Hydrogens on the nitrogen can be substituted with alkyl groups. 

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