Hydrogen compounds, active

Anion exchange resins of the quaternary ammonium hydroxide type (e.g., De-Acidlte FF, IRA-400 or Dowex I) are strong bases and are useful cataly s for the cyanoethylatlon of alcohols and possibly of other active hydrogen compounds. 

Developments in aliphatic isocyanates include the synthesis of polymeric aliphatic isocyanates and masked or blocked diisocyanates for appflcafions in which volatility or reactivity ate of concern. Polymeric aliphatic isocyanates ate made by copolymerizing methacrylic acid derivatives, such as 2-isocyanatoethyl methacrylate, and styrene [100-42-5] (100). Blocked isocyanates ate prepared via the reaction of the isocyanate with an active hydrogen compound, such as S-caprolactam, phenol [108-95-2] or acetone oxime. 

Phosphoms halides are subject to reactions with active hydrogen compounds and result in the elimination of hydrogen halide. They are convenient reagents in the synthesis of many esters, amides, and related compounds. However, because the involved hydrogen halide frequendy catalyzes side reactions, it is usually necessary to employ a hydrogen halide scavenger to remove the by-product. 

It is possible to use halogen-sensitive detectors in glc analysis of active hydrogen compounds by sdylating them with a halogenated sdylating agent, eg, CMDMS (9). 

Trimethylsilyloxazolidinone. This reagent can be used to silylate most active hydrogen compounds. 

The great reactivity of the sulfurane prepared by this procedure toward active hydrogen compounds, coupled with an indefinite shelf life in the absence of moisture, makes this compound a useful reagent for dehydrations,amide cleavage reactions, epoxide formation, sulfilimine syntheses, and certain oxidations and coupling reactions. 

The allophanate linkage is formed by the reaction of urethane with isocyanate, as shown in the fourth item of Fig. 1 [7], Isocyanates can react with many active hydrogen compounds. The active hydrogen of the urethane linkage is not very reactive, but if reaction temperatures get high enough (usually in excess of 100°C), or in the presence of certain allophanate catalysts, this reaction can actually become favored over the urethane reaction (see pp. 180-188 in [6]). 

Imines can be prepared in a similar manner by treatment of an active hydrogen compound with a nitroso compound ... 

If the active hydrogen compound has two or three active hydrogens, the Mannich base may condense with one or two additional molecules of aldehyde and ammonia or amine, for example. 

According to this mechanism, it is the free amine, not the salt that reacts, even in acid solution and the active-hydrogen compound (in the acid-catalyzed process) reacts as the enol when that is possible. This latter step is similar to what happens in 12-4. There is kinetic evidence for the intermediacy of the iminium ion (13). 

Reaction of active hydrogen compounds with tosyl azide... 

Addition of active hydrogen compounds to alkenes (Michael)... 

Reaction between acyl halides and active hydrogen compounds... 

Reaction between active hydrogen compounds and nitroso... 

Acylation of active hydrogen compounds followed by cleavage... 

Condensation between carboxylic esters and aldehydes or ketones Condensation between active-hydrogen compounds and aldehydes or ketones (Knoevenagel)... 

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