Acetylene and derivatives

Very short C-X bonds are also found in HCCF and HCCCl  

Only one isomer of HCN is known, but organic derivatives are of two kinds, cyanides RCN and isocyanides RNC. The latter have been formulated R-N=C, but 

The structures in the vapour state of HCN and of a number of covalent cyanides and isocyanides containing the linear systems R(M)-C-N and R(M)-N-C respectively are summarized in Table 21.8. There are two crystalline forms of HCN, 

The dipole moment of HCN is 2-6 D in benzene solution and 2-93 D in the vapour. The abnormally high dielectric constant of liquid HCN is attributed to polymerization, and there is i.r. evideiice for dimerization in an inert matrix at low temperatures.  

HCN polymerizes to a dark-red solid which on recrystallization yields almost colourless crystals of (HCN)4. This tetramer is actually diamihomaleonitrile  

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Dipicrylcarboxamide-acetylene. See under Di(N-phenylcarboxamide)-acetylene and Derivatives... 

Acetylene,Analysis.See Acetylene and Derivatives Analysis, listed after Acetylene Derivatives... 

Di (N-phenylcarboxamide)-acetylene and derivs see Bis (carboxanilide)-acetylene 2 B138 5 D1447—D1448... 

Over the zeolites mentioned above, acetophenone and propiophenone are easily and quantitatively produced from the hydration of phenyl acetylene and 1-phenylpropyne in very short periods of time, whatever zeolite is used. This result is in agreement with the special high reactivity of phenyl acetylene and derivatives towards hydration already found in homogeneous catalysis (ref.6). On the other hand, 1-hexyne and 2-hexyne, which are known to be less reactive towards hydration, are converted into the corresponding hexanones in relatively convenient yields. For example, over HM (Si/A1=8), 30% 2-hexanone is produced from 1-hexyne after one hour reaction. 

The surface acidity of zeolites appears to be an important ingredient for polymerization of acetylene and derivatives. Thus, when diazomethane was used to remove the protonic acidic sites on HZSM-5, no evidence for acetylene polymerization remained, compared to the original acidic form. ... 

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