A MNEMONIC FOR THE MONOSACCHARIDES R. H. LEARYl University of Hong Kong, Nong Kong
T H E appearance of a muemonic for aldo~es,~promptsalso be included on this alphabetical principle; a is R, the publication in a modified form of a similar aid, de- p is L. Thus the formula of, say, 0-glucose emerges vised by the author some years ago, and put forward by from the table as RRLRL. Methylpentoses fit into this scheme if their relationhim in a student j ~ u r n a l . ~All referenres in what folships to the hexoses can be remembered. Rhamnose lows are t o the D series. The mnemonic is in the form of a table showing the is maunomethylose, giving for the hydroxyl positions positions of the hydroxyl groups on the 2, 3, 4, and 5 RRLL. The same applies t o the ketoses. If fructose carbon atoms of the chain. The table is begun by is recalled as glucoketohexose, its ronfiguration can be writing the names of the four pentoses in alphabetical deduced. The table is easily learned, and can he reproduced in order, and fitting the tetroses and hexoses to them For the hexoses, each pair of epimersis written in alpha- less than one minute. I t might be argued that it is betical order, e. g., galactose before talose. The posi- more useful for the student to deduce these configurations of the hydroxyls are then put in (Right or Left). tions logically from the glyceraldehydes on the basis of For the 5,4,and 3 atoms we thus obtain RRRR, RLRL, the interrelationships between the compounds. UnLLRR, three easily-remembered progressions. (In fortunately it is not possible so to deduce the names; the case of the tetroses, column 3 is rejected.) The and this is where a mnemonic finds its justification. situation a t the 2-atom is somewhat different, for it is ACKNOWLEDGMENT the configuration here that determines which of the The author is grateful to Professor J. E. Driver for epimeric pair the hexose will be. It can be seen that the (alphabetically) first member of each pair is R, the his help in the preparation of this paper. second L. The a and p forms (carbon number 1) can
The University, Nedlands, Western Aus1 Present address: tralia. DELOACE, W. S., AND A. BUNDON,J. CHEM.EDUC., 32, 136
LEARY,R. H., Scope, 3.26 (1948).
GIueose-Mannose Galactme-Talose Allose-Altrose Gulose--1dose
R R R R
R L L R R L R L
R-L R-L R-L R-L