RT
xv.
A . TAYLOR
. n r i s. F.
ACREE
I n taking up the study of the mechanism of the reactions involved in the osidation and reduction of sugars and their derivatives, i t became necessary to study the equilibrium between the sugar acids and their dehydration products, including the lactones In attempting t o determine the solubility of mucic acid in water we found t h a t some lactone was formed in the solution a t once and that the amount of lactone was greatly increased if the solution were boiled. We also saw t h a t after some time equilibrium was established between the acid and lactone. A quantitatil-e study of this equilibrium was then taken up. I n this work we made up three different solutions of mucic acid a t diEerent temperatures. I n all three instances we had an excess of acid present. The first was made up at room temperature, the second was kept a t 30" for one hour, and the third a t 100' for 30 minutes. A11 three were placed in a constant temperature bath a t 2 j " and shaken from time to time. Measured quantities were withdrawn from each for titration after definite time periods. A piece of filter paper was tied over the end of the pipette to keep the solid particles of acid from being drawn up. It was found t h a t if the solution were poured into ice water the mucic acid could be titrated with standard alkali without affecting the lactone. T o determine the amount of lactone present in the solution a n excess of standard alkali was added, the solution boiled for a few minutes, and the excess alkali tritated with N I O hydrochloric acid. Phenolphthalein was used as the indicator. I n the following table we give the time t in hours, the 1
versity.
Contribution from t h e Chemical Laboratory of Johns Hopkins Uni-
amount of N I O alkali necessary t o neutralize t h e free acid and the amount necessary t o neutralize the lactcne The amount of the solutions withdrawn for titration was. in each Case, 2 j CC. Solution Xade Up at Room Temperature Cc alkali necessary t o neutralize lactone
Cc alkali necessary t o neutralize acid
t
2
4.5 28.j 52 IO0
I72
1.63
0.25
I .7 0
0.68 0.81
1.6j I .60 I .62 1 64
I .00 I . 16 I .46
258
I.jj
1.8j
720
1.53 I .6j
2.13 3.39
I440
Solution Kept a t 30' for Cc alkali necessary to neutralize acid
t
I
Hour Cc alkali necessary t o neutralize lactone
3 26 50 74 146
I .90 I .82 I .68 I .67
I .20
242
I .6j
I440
I .6j
I .69 3.21
0.80
0.78 0.90
I .7 0
Solution Kept a t
100'
I .
42
for 30 5finutes
_ __
_-~ Cc alkali necessary to neutralize acid
t
3 5
20.93
27
11.I2
51
19.63
Cc alkali necessary t o neutralize lactone
19.07 18.9j 19 5 0
8.46
17.02
7.12
171
6. 0 0
267 I440 2 880
5.40
1j.62 16.75 14.55
3.76 I .66
9.99 3.42
99
I20
Itr. A. Taj'lor and S. F . Acree
From these data it is seen that practically the same equilibrium is reached in all three experiments, the first two solutions taking 1,440 hours, while for the third it required 2,880 hours, because of supersaturation phenomena. At equilibrium it required I . 6 j cc of alkali to neutralize the free acid and an average of 3 34 cc to neutralize the lactone, so t h a t there are almost exactly twice as many lactone groups as of the carboxyl groups in the solution. It will also be seen from the table t h a t the amount of acid in the first two solutions remains nearly constant throughout, while the amount of lactone steadily increases. In the third solution both the acid and lactone gradually decrease in amount. Whether this lactone is the mono- or di-lactone, or both, we cannot tell from the data but we shall investigate the reaction velocities of the mucic acid, its mono-lactone, and its di-lactone, and shall study some of the monobasic acids to follow the rate of formation of the lactone in those cases in which we can have only the mono compound resulting. A h . B. A. Beatty is continuing this investigation under our joint direction, by the use of both conductivity methods and those outlined above, in order to learn whether acids catalyze these changes through the action of the hydrogen ions, or the nonionized molecules, or both. Depertrrtelzt of Chemistry o f Forest Products C-niversity of Wisconsin Xadison
