THE INFLUENCE OF SOLVENT AND OF CONCENTRATION

ON THE OPTICAL ROTATION OF THE PENTACETATES OF GLUCOSE AND MANNOSE.

BY P. A. LEVENE AND ISAAC BENCOWITZ.

(From ihe Laboratories of The Rockefeller Institute for Medical Research, New York.)

(Received for publication, March 28,, 1927.)

It has been known for a long time that the magnitude of the optical rotation of a given substance is a variable depending upon external conditions. Among these, concentration, solvent, and temperature are of major importance. Comparing the rotations of two epimeric substances containing in their molecules only 1 asymmetric carbon atom, it is found that the numerical values of the rotations of each epimer are identical for a given solvent and for a given concentration and that the differences are only in the direction of the rotation, one epimer rotating to the right and the other to the left. The question arises as to the behavior of sub- stances with more than 1 asymmetric carbon atom, such as sugars. It was shown by Hudson* that the numerical values of the rota- tions of certain sugar derivatives may be regarded on the basis of van? Hoff’s superposition theory as the algebraic sum of the rotations of the individual carbon atoms. Hudson has based on this conception a method of differentiation between the CY and p forms of sugars and Levene2 later showed that the same conception may serve as a basis for a method of differentiating between the configurations of individual carbon atoms of a pair of epimeric sugar acids. Observations on the Q! and P forms of sugars have brought to light the exceptional behaviour of some sugars, and in recent years Hudson3 and also Levene4 have made an effort

1 Hudson, C. S., J. Am. Chem. Sot., 1909, xxxi, 66. 2 Levene, P. A., J. Biol. Chem., 1915, xxiii, 146. 3 Hudson, C. S., J. Am. Chem. Sot., 1926, xlviii, 1424. 4 Levene, P. A., and Sobotka, H., J. Biol. Chem., 1926, lxvii, 759,771.

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680 Pentacetates of Glucose and Mannose

to connect the abnormal optical behavior with the peculiarities of the la&al structure of the exceptional sugars. However, before proceeding further in this direction it seemed desirable to answer the following question: Are the rotations of each asymmetric carbon atom of a molecule inffuenced by a given solvent in the identical manner or does the influence vary from carbon to carbon atom depending upon the configuration of the entire molecule or upon the differences in ring structure? Some suggestion as to the possibility of individual influence of the solvent on each carbon atom may be found in the observation of Levene and Meyer5 on the influence on rotation of the methylation of the individual car- bon atoms of gluconic acid.

The present investigation deals with the influence of solvents and of concentrations on the rotations of the pentacetates of glucose and of mannose. These two sugars were selected for the reason that one (glucose) behaves normally according to the rule of Hudson and the second abnormally, whereas structurally they are a pair of epimers.

The rotation of glucose pentacetate has already been measured in several solvents by Hudson and Dale.6 Their observations were limited to low concentrations. In the present investigation the concentrations were varied from about 2 to 80 per cent where solubility permitted.

The results are tabulated in Table I and are graphically rep- resented by curves in Figs. 1 and 2. In Columns 1, 3, and 5 are given the concentrations in gm. per cc., the rotations being meas- ured in tubes of 1,2, and 4 dm., depending upon the sugar and the concentration. It was so planned that in no case was the total rotation less than 7”. The numerical values of observed rotations divided by the length of the tube are given in Columns 2,4, and 6 of Table I.

These results are shown graphically in Figs. 1 and 2 where the concentrations as given in Table I are plotted as abscissae and the rotations in degrees per 1 dm. tube as ordinates.

From these curves, plotted on a large scale (commensurate with the experimental precision), the rotations at round concentrations

c Levene, P. A., andMeyer, G. M., J. Biol. Chem., 1925, lxv, 535. 6 Hudson, C. S., and Dale, J. K., J. Am. CRem. Xoc., 1915, xxxvii, 1264.

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TABLE I.

Optical Rotations of the o(- and fl-Pentacetates of Mannose and Glucose in Different Solvents and at Diferent Concentrations.

t = 25.0” zk 0.1” X = 5461 B 1 = ldm.

Chloroform. Acetone. Benzene.

Concentration Concentration Concentration in gm. per a in gm. per a in gm. per a cc. x 102. cc. x 102. cc. x 102.

(1) (2) (3) (4) (5) (6)

2.913 1.88 4.300 2.77 7.750 5.12 8.550 5.64 9.562 6.33

15.66 10.32 18.40 12.05 18.60 12.15 19.90 12.99 24.10 15.30 30.95 19.18 45.80 27.60 60.78 36.08 80.33 47.16

5.96 6.95 5.28 7.58 8.86 8.04 9.42 11.00 8.89

11.50 13.42 13.07 14.85 17.32 16.41 20.12 23.48 19.69 25.28 29.68 24.22 29.90 35.55 27.93 31.00 36.35 31.28 36.78 43.60 34.65 43.19 51.36 38.67

A. or-Mannose pentacetate.

-

2.306 3.520 6.480 7.440

14.35 14.80 22.49 26.57 31.41 33.29 35.35 49.98 68.71

degmes 1.33 2.12 3.79 4.36 8.65 8.92

13.55 15.96 18.68 19.64 20.91 28.76 38.99

- B. cr-Glucose pentacetate.

6.59 10.08 11.14 16.41 20.68 24.74 30.49 35.08 39.34 43.56 48.33

- 5.67 6.32 8.81 9.01 9.56 10.66

13.46 15.04 15.15 16.89 17.66 19.84 19.73 22.31 26.15 29.88 28.26 32.20

2.111 -0.59 9.944 -2.82

10.73 -3.05 22.86 -6.53 28.70 -8.19 37.37 -10.71 42.87 -12.35 58.77 -16.97

5.054 -1.63 7.996 -2.61

11.27 -3.68 13.49 -4.42 20.96 -6.85 27.79 -9.04 34.70 -11.22 43.62 -14.07 44.89 -14.46

6.03 8.03 9.12

13.41 14.84 21.29 25.03 29.58

-

C. &Mannose pentacetate.

degws 4.23 5.64 6.39 9.38

10.40 14.77 17.28 20.06

4.948 -1.77 7.142 -2.54 9.83 -3.49

15.56 -5.32 16.27 -5.54 20.01 -6.76 27.94 -9.33

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Chloroform. Acetone. I B0WSXlk?.

Cbncentretion in gm. per 01 cc. x 102.

(1) (2)

TABLE I-Concluded.

Concentration in gm. per n cc. x 102.

(3) I (4)

kncentration in gm. per a cc. x 102.

C.5) (6)

D. @-Glucose pentacetate.

degrees degrees

5.28 0.29 6.346 0.485 7.832 0.42s 6.661 0.50

10.99 0.59 9.67 0.73 14.87 0.80 14.93 1.15 18.70 0.995 18.39 1.46 31.26 1.75 19.24 1.53 35.10 2.02 24.79 2.01 41.69 2.48 26.82 2.14 46.19 2.80 31.59 2.61

Glacial acetic. M&by1 alcohol.

Concentration a in degrees in gm. per cc. x 10%.

P-Jbzm. Concentration ajer$5rF

in gm. per co. x 102. tube. ’

degrees

8.36 4.00 9.86 4.70

12.05 5.07

Pyridine.

kmntration OL in degrees in gm. per cc. x 102.

Pe;ib;m.

E. or-Mannose pentacetate.

7.495 4.75 7.102 4.54 6.700 3.76 8.432

! 5.30

I 8.352 5.36 8.265 4.64

9.281 5.84 9.701 6.21 9.325 5.24

cr-Glucose pentacetate.

7.852 9.78 8.01 6.672 7.16 8.315 10.32 10.20 8.363 8.98 9.244 11.48 10.83 9.662 10.39

@-Mannose pentacetate.

Concentration o( in degrees Concentration OL in degrees Concentration OL in degrees in gm. per Pefzb;m. in gm. per in gm. per cc. x 102. co. x 102.

Pe;2b;p1. cc. x 10%.

Pe;;bdm.

8.528 -5.32 6.796 -4.28 5.961 -4.72 9.610 -6.06 7.963 -4.86 7.009 -5.60

10.555 -6.68 9.601 -5.84 8.404 -6.65

P-Glucose pentacetate.

Concentration *jtr $errea in gm. per

tube. ’ cc. x 102.

Concentration a in degrees in gm. per per 4 dm. cc. x 102. tube.

7.939 1.74 7.081 -0.97 8.007 1.74 8.097 -1.21 9.402 4.08 10.65 -1.45

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P. A. Levene and I. Bencowitz 683

FIG. 1. Optical rotations of the pentacetates of cu-glucose (upper group), and cr-mannose (lower group) in different solvents. In Figs. 1 and 2 the double circles indicate points of inflection; not all of these are experimentally determined points.

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684 Pentacetates of Glucose and Mannose

were interpolated. The values thus obtained are given in Col- umns 2, 5, and 8 of Table II. The specific and the molecular rotations calculated from these values are recorded in the col- umns headed [a] and [M] respectively.

FIG. 2. Optical rotations of the pentacetates of p-glucose (upper five curves) and &mannose (lower six curves) in different solvents.

The differences between the 01 and p forms of the same sugar in the same solvent and concentration are given in Table III.

The analysis of the curves representing the rotations of the solutions as a function of concentration reveals certain very sig- nificant peculiarities. First, practically all the curves show at a certain concentration a break, after which the curve assumes a new

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P. A. Levene and I. Bencowitz 685

slope. Second, the curves expressing the rotations in individual solvents do not run parallel to each other, but diverge with increase in concentration. Third, the specific rotations remain practically constant in dilute solutions and change markedly with increase in concentration. This point is shown in Fig. 3 where the molecular rotations are plotted as ordinates and the concentrations as ab-

TABLE II.

Rotatory Power at Round Concentrations.

t = 25.0” i 0.1” X = 5461 d I = ldm.

COIMII- Chloroform. Acetone. BMlZC?ll~. tration in gm. perec. a x IO’.

(1) (2)

2.0 4.0 6.0 8.0

10.0 12.0 14.0 16.0 18.0 18.6 20.0 20.4 22.0 24.0 25.0 26.1 30.0 35.0 40.0 45.0 50.0 60.0 70.0 80.0

1.28 250.0 64.0 1.12 218.4 2.50 243.8 65.5 2.34 228.1 3.90 253.6 65.0 3.57 232.0 5.22 254.5 65.3 4.77 232.6 6.52 254.4 65.2 6.00 234.0 7.86 254.9 65.5 7.21 233.8 9.17 255.4 65.5 3.42 234.6

10.45 255.4 65.3 9.62 234.5 11.69* 253.8 64.9 10.62 234.5 12.16 255. o 65.4 11.20 234.8 12.95 252.6 64.7 12.03 234.6

14.08 249.6 15.21 247.2 15.72 250.9

18.62 242. I 21.46 239.1 24.26 236.5 27.14 235.2 29.96 233., 35.65 231.7 41.31 230.2 46.90 228.6

64.0 13.23 234.5 63.4 14.44 234.6 62.8 15.04 234.6

15.75* 235.3 62.0 17.84 231.9 61.3 20.58 229.3 60.6 23.31 227.3 60.3 26.05 225.8 59.9 28.78 224.5 59.4 34.21 222.4 59.0 58.6

- A. cu-Mannose pentacetate.

56.0 1.40 273.0 58.5 2.81 274.0 59.5 4.21 273.0 59.6 5.62 274.0 60.0 7.07 275.r 60.0 8.41 272.1 60.1 9.82 273.6 60.1 11.20 273.0 60.1 12.52 271.3 60.2 12.96 271.1 60.1 13.95 272.0

14.22* 271.8 60.1 15.23 270.0 60.2 16.52 268.5 60.2 17.14 267.4 60.3 59.5 20.36 264.4 58.8 58.3 57.9 57.6 57.0

1 I

70.0 70.3 70.2 70.2 70.7 70.7 70.1 70.0 69.6 69.1 69.8 69.7 69.2 68.3 68.5

67.9

* The concentration at which there is an inflection in the curve.

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TABLE II-Continued.

2.0 2.30 448.6 115.0 2.50 487.6 125.0 2.23 434.8 111.5 4.0 4.67 455.3 116.7 5.00 487.5 125.0 4.46 434.8 111.5 6.0 7.03 456.9 117.2 7.56 487.5 125.0 6.69 434.8 111.5 8.0 9.37 456.8 117.1 10.03 488.9 125.3 8.94 435.8 111.7

10.0 11.68 455.1 116.8 12.54 489.1 125.4 11.16 435.2 111.6 12.0 14.00 455.0 116.6 15.06 489.4 125.5 13.38 434.8 111.5 13.05 15.20* 454.2 116.5 14.0 16.31 454.3 117.0 17.59 490.0 125.6 15.61 434.8 111.5 16.0 18.68 455.9 116.7 20.14 490.9 125.9 17.88 435.8 111.7 18.0 21.04 455.9 116.8 22.64 490.5 125.8 20.25 438.1 112.5 20.0 23.40 456.3 117.0 25.14 490.2 125.7 22.60 440.1 113.0 22.0 25.79 457.2 117.2 27.64 490.0 125.6 24.93 441.9 113.3 24.0 28.20 458.1 117.5 30.15 489.9 125.6 27.27 443.1 113.6. 26.0 30.60 459.0 117.7 32.68 490.2 125.7 29.60 444.,, 113.8 28.0 33.00 459.6 117.9 35.18 490.0 125.6 31.90 444.3 113.9 30.0 35.42 460.4 118.1 37.66 489.6 125.5 35.0 41.40 461.3 118.3 43.92 489.4 125.5 39.0 46.29 462. g 118.7 48.96 489.6 125.5 44.0 52.30 463.6 118.9

3.0 5.0 7.0 9.0 9.9 -

12.0 15.0 16.8

18.0 21.0 22.2 24.0 27.0 30.0 35.0 40.0 45.0 50.0 55.0

0.85 110.6 28.3 0.96 124.8 32.0 1.08 140.4 1.41 110.0 28.2 1.62 126.4 32.4 1.79 139.6 1.97 109.8 28.1 2.28 127.8 32.6 2.48 138.5 2.54 110.1 28.2 2.95 127.8 32.81 3.20 138.7

3.40 110.6 4.26 110.8

5.09 llO.?, 5.94 110.3 6.29* 110 6

6.82 110.8 7.69 110.8 8.57 111.4

10.02 111.6 11.49 112.0 12.94 112.1 14.40 112.3 15.86 1112.6 ___~

28.3 3.93 127.1 28.4 4.94 128.4

5.52* 128 _ 1 28.3 5.90 127.x 28.3 6.87 127.6 28 3

28.5

28.61 28.5’

7.84 127.4

9.75 8.82 127.4 1‘26.7 28.6, 11.32 126.1 28.7; 12.90 125.8 28.7, 14.50 125.7 28.8 28.8; -

686

32.9 5.15 133.9 32.6

32.7 6.11 132.4 32.6 7.08 131.5

32.7! 8.06 131.0 32.7 9.03 130.4 32.5~ 32.6’

10.01 130.1

32.2’ 32.2

I I

C. @-Mannose pentacetate.

36.t 35.j 35.: 35.: 3.5 ‘ ‘

34.1 34.:

33.! 33.:

33.1 33.1 33.‘

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TABLE II-continued.

Concen- tration

Chloroform. Acetone. BHlZ~~~.

D. p-Glucose pentacetate.

2.0 4.0 5.0 7.0 9.0

10.0 12.0 12.2 14.0 16.0 18.0 20.0 22.0 25.0 .27.0 29.0 32.0 35.0 40.0 45.0

.- c oncen- trati'on in gm. per cc. x.102.

-

0.120 23.4 0.22s 2119 0.280 21.8 0.385 21.4 0.480 20.8 0.540 21.0 0.64s 21.0

0.748 20.8 0.855 20.8 0.960 20.8 1.060 20.6, 1.160 20.56 1.320* 20.59 1.45s 21.02 1.595 21.4, 1.806 22.00 2.020 22.51 2.362 23.0~ 2.713 23.51

6.0 0.150 5.6~ 0.302 5.6 0.375 5.5 0.525 5.3 0.680 5.4 0.750 5.4 0.900

0.920* 5.3 1.071 5.3 1.244 5.3 1.420 5.3 1.599 5.3 1.776 5.3 2.03s 5.4 2.210 5.5 2.382 5.6 2.640 5.8 5.9 6.0

29.2 7.5' 0.095 29.4 7.5 0.190 29.2 7.5 0.240 29.2 7.5 0.335 29.4, 7.5 0.430 29.2 7.5 0.485 29.2 7.5 0.575 29.4 7.5 29.8 7.6 0.665 30.3 7.8 39.77 7.9 31.18 8.0 31.47 8.1 31.76 8.1 31.92 8.2 32.78 8.2 32.92 8.3

18.50 18.50 18.70 18.66 18.63 18.72 18.69

18.52

- 4.7 4.7 4.8 4.9 4.8 4.8 4.8

4.7

- Glacial acetic acid. Methyl alcohoi. Pyridine.

2.0 1.24 241.8 62.0 1.29 251.5 64.5 1.12 218.4 56.0 4.0 2.51 244.5 62.7 2.56 249.6 64.0 2.24 218.4 56.0 6.0 3.76 240.6 61.7 3.84 249.6 64.0 3.37 218.8 56.1 8.0 5.04 245.7 63.0 5.12 249.6 64.0 4.48 218.4 56.0

10.0 6.28 244.9 62.8 6.40 249.6 64.0 5.61 218.8 56.1

a-Glucose pentacetate.

E. or-Mannose pentacetate.

2.0 2.48 483.6 124.0 2.40 468.1 120.0, 2.13 417.3 107.0 4.0 4.96 483.6 124.0 4.81 468.1 120.0 4.28 417.3 107.0 6.0 7.45 483.6 124.0 7.22 468.1 120.0 6.43 417.3 107.0 8.0 9.93 483.6 124.0 9.64 468.1 120.0 8.58 417.3 107.0

10.0 12.42 1483.6 124.0 12.08 471.9 121.0i 10.65 417.3 107.0

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688 Pentacetates of Glucose and Mannose

TABLE II-COnCkLded.

ChKXXl- Glacial acetic acid. Methyl alcohol. Pyridine. tration

5 ,1, ) 6 1 ::: ,, 1 ;; 1 :I d, 1 : ; ,:“o:

fl-Mannose pentacetate.

2.0 -0.623 121.3 31.1 -0.608 118.55 30.4 -0.79s 154.8 39.7 4.0 -1.250 122.4 31.4 -1.201 117.00 30.0 -1.582 154.4 39.6 6.0 -1.89~ 123.2 31.6 -1.827 118.56 30.4-2.37s 154.4 39.6 8.0 -2.530 123.2 31.6 -2.43.~ 118.55 30.4 -3.162 154.1 39.5

10.0 -3.16~ 123.2 31.6 -3.050 118.9~ 30.5 -3.960 154.4 39.6

2.0 0.221 4.0 0.440 6.0 0.662 8.0 0.880

10.0 1.100

42.90 42.90 42.90 42.90 42.90

- fi-Glucose pentacetate.

11.0 -0.135 11.0 -0.262 11.0 -0.405 11.0 -0.54s 11.0 -0.692

- 26.13 25.74 26.13 26.52 26.91

6.7 6.6 6.7 6.8 6.9

scissa3. Fourth, the numerical values of the specific rotation as a function of the solvent can be arranged in the following order.

A. For the a: and p forms of glucose pentacetate the order is: acetone > glacial acetic acid > methyl alcohol > chloroform > benzene > pyridine.

B. The order for the pentacetates of mannose is, for the a form: benzene > chloroform > methyl alcohol > glacial acetic acid > acetone > pyridine; for the p form; chloroform > methyl alcohol > glacial acetic acid > acetone > benzene > pyridine.

In this connection emphasis should be placed on the fact that the order of solvent influence on rotation in the mannose pentace- tates is different from that in the two glucose pentacetates, and furthermore, that it is different in each of the two mannose pen- tacetates. In the case of the two a! forms, the order is the same, but in the opposite sense as shown in Fig. 4. An exceptional posi- tion is occupied bypyridine. In this solvent all forms show the lowest rotations.

Each of the four observations has its own significance. From the first observation one may conclude that the relationship be- tween solvent and solute changes with increase in concentration.

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P. A. Levene and I. Bencowitz 689

As yet there do not exist sufficient data to offer a definite explana- tion of that relationship. It may be of a chemical nature, the solvent forming a complex with the solute. The ratio of the com- plex molecules to the simple may change with the increase in con-

TABLE III.

Differences between [a]t, of a- and B-Mannose Pentacetates and CL- and B-Glucose Pentacetates at Round Concentrations.

concentra tion in

gm. per CO.XlO~.

3.0 92.3 5.0 93.7 7.0 93.6 9.0 93.4

10.0 93.4 12.0 93.8 14.0 93.8 16.0 93.7 18.0 93.2 20.0 93.7 22.0 93.0 24.0 91.9 25.0 91.3 30.0 90.7 35.0 89.9 40.0 89.3 45.0 89.0 50.0 88.7 55.0 88.4

( Xacial acetic acid.

2.5 62.4 5.0 62.8 7.5 62.6

10.0 62.6

( :hloroform Acetone.

Mannose pentacetates. bi, - I&q

89.3 91.7 92.1 92.6 92.8 92.8 93.0 93.0 92.8 92.7 92.7 92.9 92.9 92.0 91.4 90.5 90.1

_-

-

-

..-

-

BCW.elle.

106.0 106.0 105.7 105.7 105.6 104.9 104.3 104.3 104.5 103.6 102.9 102.4 102.3 101.3

-

_ c

Glucose pentacetates. Eel, - [aI8

:hloroform Acetone.

110.2 111.4 111.6 111.7 110.4 110.3 111.7 111.4 111.5 111.7 112.0 112.2 112.3 112.5 112.5 112.8 112.8

117.5 117.5 117.6 117.8 117.9 118.0 118.0 118.1 117.9 117.7 117.6 117.5 117.5 117.3 117.2

106.8 106.8 106.8 106.9 106.8 106.7 106.7

Pyridine. Glacial acetic acid. Pyridine.

96.0 113.6 112.8 95.6 112.8 113.2 95.4 112.6 112.6 95.4 113.0 114.0

centration. It may also be assumed that the solvent is attached to different atoms or groups of the solute depending upon the concentration. In fact, it has been shown that pentacetate of glucose forms a definite compound with benzene7 and also with

7 Mall van Charante, J., Rec. trav. chim. Pays-Bas, 1902, xxi, 42.

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-3 1% Ib io U-J 60 10 80 Ccxw%mtioit” in gm/iE, X Xl2

FIG. 3. Molecular rotations of the pentacetates of oI- and &glucose and of 01- and p-mannose in different solvents.

cr-Glucose pentacetate in benzene [Ml scale, O.K. “ “ “ chloroform “ “ add 10. “ ‘I ” acetone “ “ “ 30.

p-Glucose “ “ all solvents “ “ O.K. cu-Mannose “ ‘I benzene “ “ “

I‘ ‘I “ acetone “ “ subtract 2. “ “ ‘I chloroform “ “ “ 12.

@Mannose “ “ acetone “ “ O.K. “ “ ” chloroform “ “ “ ‘< “ “ benzene “ “ add 10.

690

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12.00

10.00

3

5 8.00

-2 3

5 a 6.00

A

4D0,

I

2.00

0.00

P. A. Levene and I. Bencowitz 691

L

5.0 ’

I 1

-1

zhloroform 2 Methyl alcohol 3

1

Concf2ntration in gm/c~. X 10’

FIG. 4. The effect of solvents on the optical rotation of the pentacetates ofor-glucose (upper group) anda-mannose (lower group).

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692 Pentacetates of Glucose and Mannose

pyridine.8 On the other hand, the influence of the solvent may be entirely external, affecting the degree of deformation of the solute.

From the second observation it may be concluded that each solvent forms a different complex with the solute or that it brings about a different form of distortion of the molecule of the solute.

The third observation needs no special discussion in the light of the first two. However, it emphasizes a practical point; namely, that in the comparative study of the numerical relationships of the rotations of different sugars, those series of concentrations should be selected in which the specific rotations remain constant.

On the fourth observation centers the principal interest of the present investigation. It demonstrates that there exists a diver- gence in the influence of the solvents on the pentacetates of glucose as compared with the influence on the pentacetates of mannose. The differences are marked not only in regard to the respective specific rotations, but also in regard to the differences in the rota- tions of the a! and /3 forms.

Hudson6 and his coworkers have shown that with respect to the latter value the glucose pentacetates behave normally. In his latest publication Hudson3 assigns to them the < 1,4 > structure. In the same publication Hudson assigns to /3-mannose pentacetate the < 1,4 > structure and referring to the a! form he remarks: “For the present the acetate of +55 rotation will be left unclas- sified; the determination of its ring form and even the question whether it may not be a mixture of substances remain outstanding problems.“9 Levene and Sobotka,4 on the other hand, on the basis of a comparative study of the rotations of the pentacetates of glucose, galactose, and mannose, were inclined to assign to the pentacetates of glucose the <1,4> ring and to those of mannose the < 1,5 > ring.

If a classification of pentacetates should be made on the basis of the order of influence of the solvent, the conclusion would necessarily be reached that the a- and p-glucose pentacetates be- long to one type of structure, and that the a! and p forms of mannose pentacetate belong to two different types, each distinct from that of the glucose pentacetates.

* Behrend, R., Ann. Chem., 1907, cccliii, 106. Q The italics are ours.

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P. A. Levene and I. Bencowitz 693

On the other hand, if the differentiation of the pentacetates should be made on the basis of the differences of the molecular rotations of the a: and p forms, then one will be confronted with the following confusing facts.

[Ml, - [M]p glucose pentacetate The ratios Of [Ml, - [&JIB mannose pentacetate differ in indi-

vidual solvents in the following way: chloroform 0.84, acetone 0.78, pyridine 0.85, glacial acetic acid 0.55, benzene 1.0.

Thus, if the conclusion was based on an observation in a single solvent the classification would depend on chance. In benzene the differences of the rotations of glucose pentacetate and of mannose pentacetate have the same numerical value; in glacial acetic acid the divergence is the greatest. In the other solvents the values are approximately in the middle of the distance be- tween the two extreme values.

Thus, it seems suggestive that both the OL and /3 forms of man- nose pentacetate belong to a different type from that of the glucose pentacetates and it is also possible that the two forms of mannose pentacetate have ring structures differing from each other as was suggested by Hudson.

More information on the influence of various solvents on the rotations of epimeric sugar derivatives is needed before a final conclusion can be reached as to the structural relationships of the pentacetates of glucose and mannose. As yet, the problem is not definitely settled.

EXPERIMENTAL.

A Schmidt and Haensch polarimeter supplied with a large direct vision spectroscope as a monochromator was used in this work. A quartz omercury lamp served as a source of light. The green line 5461 A was employed. The purity of this light, as well as the accuracy of the polarimeter, was tested by means of a quartz test plate recently calibrated at the Bureau of Standards. Jacketed tubes were employed throughout and a rapid stream of water from a regulated thermostat maintained a constant temperature of 25.0” zt 0.1”.

The solutions were made up by weighing the solids directly in 10, 15, or 25 cc. flasks. The solvent was then added up to the cali- bration mark. The flasks were carefully calibrated at 25.0°,

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694 Pentacetates of Glucose and Mannose

and in making up the solutions the solvent was brought up to mark only after the solution and the flask had been allowed to come to the proper temperature. Extra pains were taken in making up these solutions inasmuch as t,he total volume of solvent was small and a slight error in the volume made appreciable discrepancies in the final result.

Throughout this research the same sample of substance was used in the case of Q(- and P-glucose pentacetates and @-mannose pen- tacetate. In the case of the a+mannose pentacetate, however, we were obliged to use several samples. From these, only those giving the highest rotations were used.

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P. A. Levene and Isaac BencowitzOF GLUCOSE AND MANNOSE

ROTATION OF THE PENTACETATESCONCENTRATION ON THE OPTICAL

THE INFLUENCE OF SOLVENT AND OF

1927, 73:679-694.J. Biol. Chem. 

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