Methylamine physical properties

Methylamines, 12 112 16 355-370 chemical properties of, 16 357-360 commercial, 16 356t economic aspects, specifications, and uses for, 16 364-368 end uses of, 16 365 exposure limits for, 16 3641 as feedstocks, 16 357-359 health, safety, and toxicology of, 16 364 manufacture of, 16 360-363 manufacturing data for, 16 367t physical properties of, 16 356-357 production of, 16 300 products manufactured using, 16 366-367t... 

Methylamines are colorless liquids that are volatile at normal atmospheric conditions. They have threshold odor limits of less than 10 ppm, and at low concentrations they have a fishy smell. At high concentrations they smell like ammonia. The physical properties are given in Table 14.1 and Table 14.2. 

From the meager data available, the observed analogy in the variation of the conductance in the methyl amine solutions with concentration and temperature with that in the ammonia solutions suggests a close similarity in the constitution of both solutions, as also do the optical data discussed in Part III-B. The observed conductance in methylamine solutions with concentration greater than 0.3M is smaller by about a factor of 100 than the conductance in the corresponding ammonia solutions. This can probably be explained by the smaller solubility of the metals in amine solutions. This would lead to a larger value for the number of methylamine molecules per atom of metal dissolved relative to ammonia solutions (about 6 in saturated sodium-ammonia solutions as compared to 23 in sodium solutions in methylamine). However, in very dilute solutions, the smaller value of the equivalent conductance in the methylamine solutions would have to be explained by differences in physical properties such as viscosity and dielectric constant of ammonia and methylamine. 

They are very soluble in water, alcohols, ethers, and most polar solvents. At low temperatures, aqueous methylamines form crystalline hydrates CH3NH2-3H20, (CH3)2NH 7H2O, and (CH3)3N IOH2O. In the presence of ammonia, methylamines react explosively with mercury so instruments containing mercury should not be used on methylamines. The amines also are flammable in air. Their flammability ranges as well as some of their important physical properties are listed in Tables 28.16 and 28.17. 

Other Physical Properties.—Conformational information for thiols and sulphides can be obtained from enthalpy of formation data. Proton-transfer of benzyl-mercaptan (protonation at sulphur with CF3SO3H, and de-protonation by imidazole) has been studied. Thermodynamic parameters for acidity constants of substituted benzenethiols, and for hydrogen-bonding interactions between alkanols and di-n-octyl sulphide and the analogous ether and N-methylamine, reveal a dominant electronic influence of the orM<>-substituent, and substantially higher hydrogen-bond acceptor ability for the aliphatic sulphide than is generally assumed. ... 

Physical Processes foe Separating Metirylammes. Since the cost of separating methylamines is a major item, much effort has been put into developing separation processes. There are numerous patented separation procedures based on the differences in the phytical and chemical properties of these products. For example, Babcock found that the vapor-pressure curve of trimethylamine does not parallel the practically parallti curves of NH , mono- and dimethylamine. It intersects the dimethylamine curve at about 55 psia, and furthermore, when a mixture of trimethylamine and dimethylamine is distilled above this pressure, a dimethylamine-rich... 

Dimethylamine, (CH3)2NH, is a representative of the class of secondary amines. It resembles closely methylamine in physical and chemical properties. It is a gas, with a strong, fishy odor, and can be condensed to a liquid which boils at 7.2° it is found in herring brine. It is formed when methyl iodide is heated with ammonia. Methylamine is first formed and then converted into dimethylamine. The first reaction consists in the addition of the halide and ammonia —... 

---