Abstract
In the paper, we discuss the phenomenon of melting and triple point properties deviations from regularity in tangent of slope and “zigzag” progression in n-alkanes, n-alcohols, n-alkanoic amines and n-alkanoic acids. The thermodynamics and chemical aspects of this intriguing phenomenon will be discussed. In graphs of melting and triple point properties of saturated alkanoic (fatty) acids, n-alcohols, n-amines and n-alkanes homologous series have been observed two segments, which are characterized by changes in tangent of slope from the fifth member of homologous series, and harmonic zigzag progression of melting and triple point temperatures and some other thermophysical parameters. The melting and triple point temperatures for even numbers of carbon atoms in homologous series of n-alkanes, n-alkanoic acids, n-alcohols, n-amines and some cyclic and polycyclic substances are larger than average values of the nearest odd numbers. A general character of this phenomenon for a wide number of substances motivates researchers to study the nature and mechanism of it and its implication.
Highlights
In pharmaceutical and food industries, the phenomenon of crystalline polymorphism of cocoa butter is well-known
In graphs of melting and triple point properties of saturated alkanoic acids, n-alcohols, n-amines and n-alkanes homologous series have been observed two segments, which are characterized by changes in tangent of slope from the fifth member of homologous series, and harmonic zigzag progression of melting and triple point temperatures and some other thermophysical parameters
The melting and triple point temperatures for even numbers of carbon atoms in homologous series of n-alkanes, n-alkanoic acids, n-alcohols, n-amines and some cyclic and polycyclic substances are larger than average values of the nearest odd numbers
Summary
In pharmaceutical and food industries, the phenomenon of crystalline polymorphism of cocoa butter is well-known. The careful comparison of melting points in several homologous series supports the perception that general differences are not the operator errors and do not result from crystal morphology of samples, but have more meaningful basis Despite of these differences some general tendencies in pure substances can be observed, such as the “zigzag” effect: a periodic alteration of some thermophysical properties added to a general smoother change. For long list of substances as: n-alkanes, n-alcohols, n-alkanoic acids, lipids and some other, different melting points, which often have significant differences, had been presented in literature for the same substance In some of these observations, the crystalline polymorphism had been pointed out as a cause for the phenomenon, but in several cases the cause was not pointed out. The possible technical applications [7] of this phenomenon and its implication will be discussed elsewhere in future papers
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
