Solution to the “never odd or even” challenge

Abstract

The winner of the ‘Never odd or even’ challenge (published in volume 413 issue 9) is: Alvaro Etcheverry Berrios, The University of Edinburgh, Edinburgh, Scotland, UK. The award entitles the winner to select a Springer book of their choice up to a value of €100,-. Our Congratulations! The well-known substance described in the never odd or even challenge [1] is oleic acid. The name derives from the Latin word oleum, meaning oil obtained from olives, the fruits of Olea europaea (Fig. 1). Oleic acid is a naturally occurring monounsaturated fatty acid with an unbranched chain of eighteen carbon atoms, with a carboxyl group at one end and a methyl group at the other end. The numbering scheme recommended by the IUPAC is indicated by counting from 1 starting from the carboxyl end. The position of the cis-configured double bond is specified by labelling the unsaturated carbon closest to the carboxyl end as shown in Formula 1 [2]. An abbreviated form of the IUPAC notation is the lipid number where oleic acid is known as 18:1(9) or cis-Δoctadecenoic acid where the capital Greek letter Δ corresponds to Roman “D”, for double bond. The IUPAC notation has the advantage of being more clear and descriptive than common lipid name nomenclature or the physiological numbering convention. In the latter, the last carbon in the chain is labelled with letter n. This ‘n − x’ nomenclature provides names of individual compounds and classifies them by their likely biosynthetic pathway. In oleic acid, the double bond is located on the 9th carbon–carbon bond, counting from the methyl end of the molecule backbone. Therefore, it is classified as n − 9 fatty acid as shown in Formula 2. In nutritional literature, the methyl end of the chain is often designated with the last letter of the Greek alphabet— omega (ω). In this convention, oleic acid is an omega−9 orω−9 fatty acid. Coincidentally, it does not matter which notation is used