The polymorphism of 13 single acid triglycerides with acyl group chain lengths ranging from 16–22 was studied by differential scanning calorimetry. In contrast to the singleβ′‐form generally attributed to such triglycerides, at least two intermediate endotherms were found for most samples between the least stable (α) and most stable (β) polymorphs. For saturated triglycerides, two versions of the familiar “tuning fork” model meet theβ′‐form requirement of alternate fatty acid chains in planes perpendicular to each other. The detection of three intermediate endotherms for triolein, tri‐cis‐1 1‐octadecenoin and trierucin (and possibly also trilinolein) may be rationalized by assuming that the segments of polymethylene chains on either side of double bonds may zigzag in different planes. Four exceptions for which no evidence was found forβ′‐forms are tri‐cis‐6‐octadecenoin, tri‐cis‐6‐hexadecenoin, tri‐trans‐6‐octadecenoin and trielaidin. Three of these exceptions contain Δ6‐acyl groups and have in common segments with even numbers of methylene groups on either side of the double bonds. These same three triglycerides also have a shorter than usual polymethylene segment between the ester linkages and the double bonds and a longer than usual distance from the double bonds to the terminal methyl groups. Tri‐trans‐6‐octadecenoin and trielaidin are exceptional in still another way. Only they and are exceptional in still another way. Only they and trierucin exhibited significant nonconformity with an empirical relationship between melting points and heats of fusion ofβ‐forms. Otherwise, all points in a plot of the former physical constants vs. the latter closely fit a smooth curve, the positive slope of which gets larger as the X‐axis values, i.e., melting points, increase.

SUNY-CortlandCortland. NY 13045 Editor's Note: One of the greatest deterrents to the adoption of microscale techniques for organic chemistry laboratory courses in many institutions is the high cost of microscale glassware. There are many experiments that can be carried out on a small scale using regular glassware as the following experiment demonstrates. Information about other experiments that meet these criteria would be appreciated and should be sent to the editor of this column.

This article suggests the use of differences in density as a means for separation and identification of plastics.

No abstract

This study was conducted out of a concern that many organic chemistry textbooks include very few industrial processes and those that are included tend to be out of date.