Methylamine hydrogen bonding

The N—H N hydrogen bond is responsible for the formation of the complexes between aniline and aliphatic amines (ammonia, methylamine, dimethylamine and tri-methylamine) which act as proton acceptors. Infrared photodissociation spectra and DFT calculation indicate208 that the clusters [aniline/ammonia]+ and [aniline/methylamine]+ have a non proton transferred (without the proton donation from the aniline moiety to the amine molecule) structure, while the complexes [aniline/dimethylamine]+, [aniline/ trimethylamine]+ possess a proton transferred structure. Reasonably, the proton transfer increases on increasing the proton affinity of the amine used as solvent. 

The antiarthritic drug naproxen (S-70) has a fully interlocked structure, but it exhibits prominent irregular channels to both sides of an infinite linear hydrogen bond array of the carboxylic groups (Fig. 2.1.55). This should make it sensitive to exposure to proper atmospheric pollutants. Indeed, crystalline 70 reacts with gaseous ammonia, methylamine, or diluted bromine without melting [70],... 

Fig. 14.08. Plan of one layer of the orthorhombic structure of methylamine, CH3. -NH2, projected on a plane perpendicular to the z axis. The nitrogen atoms are nearly coplanar, and hydrogen bonds between them are represented by broken lines. Crosses indicate the comers of the unit cell.

The length of the N---N hydrogen bond in the hexamethylenedi-amine structure, very nearly the same as that in methylamine ( 14.15), again reveals that this is a relatively weak link. It is also of interest to note that in this structure only half of the available hydrogen atoms take part in hydrogen-bond formation, for each NH2 group, potentially... 

Hydrogen bonding (a) in methylamine and (b) between methylamine and water. Dotted lines represent hydrogen bonds. 

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