294 SECTIONAL TRANSACTIONS.—B. 
a carboxylic acid but owed its acidic character to the presence of an enolic 
hydroxyl group. At this stage of the investigation (March 1933) sufficient 
chemical and crystallographic evidence had accumulated to support the 
proposal of the structural formula (I). 
HO OH O O O O COOH 
hy Sate iia Wade vie | 
=o C=C C= COOH 
a \n H 
co CO rere) COOH COOH 
Wes val ye | | 
H—¢2£o aig = RE! gree @ | + H—C—OH HO H—C— OH H-C—o 
| | | i | > 
HO HO—C—H HO—C—H HOCH mead 
| 
CH,OH CH,OH CH,OH CH,OH COOH 
(1) (II) (III) (IV) (Vv) 
It remained only to decide whether a y-(1 : 4) or a 8-(1: 5) lactone ring 
was present, and in April 1933 a clear decision in favour of the y-lactone 
structure was obtained from investigations on the tetramethyl ether of ascorbic 
acid. 'Thissubstance gives on degradative oxidation a dimethyl /-threonic acid 
which has the free hydroxyl group in the «-position. The presence of 
a y-lactone in ascorbic acid (I) was therefore definitely established. Con- 
firmation of these views was then provided by the synthesis of ascorbic 
acid from /-xylosone. : 
The chemical and physical properties of ascorbic acid are considered in 
relation to its molecular structure. 
Mr. E. Gorpon Cox.—Crystallographic contributions to the study of 
ascorbic acid. 
The unusual chemical properties of ascorbic acid are such that at an early 
stage in the study of its constitution it was possible to suggest two or three 
spatial formule, any one of which, however, could only be finally estab- 
lished or eliminated by much time-consuming study. Any additional 
experimental method which could be used to discriminate between the 
possibilities was therefore of great value. Whilst it is usually very difficult 
to prove the correctness of a given structure by the use of X-rays, it is often 
relatively easy to eliminate suggested alternatives. ‘This was found to be 
so in the present case. Of the constitutional formulz proposed only one 
was found to fit the observed optical and X-ray data. In a relatively short 
time this formula was established by chemical methods as correct. During 
this latter stage of the work, X-ray methods were again found to be of use 
in determining molecular weights and identifying degradation products, 
especially in cases where the yield was very small, or where melting point was 
uncertain. 
The next step, that of synthesis, was also assisted by crystallographic 
methods. In the early stages work was naturally on a small scale, with 
correspondingly small yields ; X-rays and microscopic examination were 
used to identify products and thus to prevent waste of time and material on 
syntheses under unfavourable conditions. 
More detailed crystallographic work on ascorbic acid and related com- 
pounds has been carried out in order to determine as far as possible some of 
the finer details of the structure. 
