A NEW RELATIONSHIP CHART OF THE CARBOHYDRATES*.~ C. W. EDDY,148 S. MISSIONROAD, LOSANGELES,CAL~ORNIA
It is well understood that the most effective means of obtaining knowledge is through the sense of sight. The adoption of charts and models in science courses to explain the ideas marked an advance over the pure lecture system of teaching. The student visualizes through the use of charts and models the idea that is endeavored to be expressed and fixes i t more distinctly in his memory, thereby retaining the idea for a longer period of time. History of the Relationship Charts A relationship chart between the hexoses and the pentoses was first constructed by the author when answering a question in a course in advanced organic chemistry. The author then saw the possibility of a more complete and legible chart and after much study and reference work, the "Relationships among the Carbohydrates" (Plate I) was formulated. Rosanoff (1)has an ingenious chart showing the relationship that exists between the simpler sugars and their reaction products. The difficulty with the chart for beginners lies in his method of explanation. He has given each class of compounds a symbol and additional symbols, suoh as dots and side arms, placed on the primary symbol indicate conlpounds formed from the primary compound. This method necessitates the memorizing of a group of symbols in order to understand and remember the existing structure and reactions.of the sugars. In the preparation of this chart as presented, the author has endeavored as much as possible to do away with symbols except as the syhbols represent the actual structure of the compounds. Relationship and Nomenclature The relationships among the different forms of sugars are based on the pioneer researches of such honored men as Emil Fischer, Werner, Wohl, Kiliana, Nef, Ruff, Lob, and many others. Their patient researches have, by many experiments, shown us the structure of the sugars as they are believed to exist (2). They have also given us the reactions by which one form of a sugar may be converted into its isomer. Cohen, Armstrong, Rosanoff, Fischer, Wohl, and others seem to disagree as to the naming of the forms of the sugars, especially between the d- and I-forms. Therefore i t has seemed reasonable to follow the more modern
* The author wishes to express his sincere thanks to his professor, Dr. H. J. Barrett, for his suggestions in the preparation of the charts and the article. t The presentation of a paper covering the essential features, uses and adaptations of the chart was given in the Division of Chemical Education, fall meeting of the Ameri3, can Chemical Society, Philadelphia, 1926. [For abstract of paper see J. CHEM.EDUC., 953 (Aug., 192G).] A similar paper was presented by the author at the 1927 meeting of the South Dakota Academy of Science. 2692
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Geneva system. The hexose sugars that are assumed to have the -OH of the fifth carbon atom on the right side of the plane figure are arbitrarily called d- and those in which the O H is assumed to be on the left side of the fifth carbon atom are arbitrarily called 1-. This naming of the d- and 1- forms does not in any sense refer to the dextro and levo rotatory power of these sugars; it is more of a means to distinguish between the mirror images of two similar isomers, e . g., d-glucose has the structure (3)
OH
CHO
HC'OH
I 1 HCOH I HCOH 1
HOCH
HCOH
I
or
CHOH
I F'
HC
I
CHIOH
'7
and 1-glucose has the structure (3) HOCH
I
HCOH
HOCH or
HOCH
I HOCH I HCOH I
1
H
CHpOH
Explanation Plan: I shows the relationship that exists between the simple sugars. The reactions which indicate the chemical changes are designated by arrows t',~atare numbered. In building up the carbon chain and passing
I1 I
C-H HOCH
I
HCOH
I
HCOH I
I I HOCH I HCOH I
II
HC-OH
,
HCN -------t
C-OH
-
HFOH
Arabinose nitrile
I
HCOH I CHzOH d-Gluconic acid
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0
0
II
0
II
COH
II
C-H
I
HCOH
I HOCH I
N o w m s n , 1930
HCOH
-HsO
I I HCOH I
HOCH
0
HCOH
I I
HCOH
HCOH
HC
I
CaOH
I
CHpOH Glucose ladone
CHZOH Glucose
from a simple sugar to the next higher one, the Kiliana (4) reaction (arm4 1) is used. To illustrate the reaction, let us take a specific example. to d-arab'mose, HCN is added, the cyanhydrin is formed which may he hydrolyzed to the d-gluconic acid. The gluconic acid tends to lose w forming the lactone which is then reduced with sodium amalgam to cose. This example is typical of all the reactions of 1. optical isomers (arrow 2) the reaction of Van Ekenstein is The aldose, take glucose for example, is heated with various alkalis whereupon the enolic and then the ethylene oxide form is produced which resrranges to mannose; mannose being the nearest optical isomer of gluco,e. An equilibrium is of course reached from which the desired hexose may be isolated by fractional crystallization of the hydrozones. 0
CH(0Hf.
I>
II C-H
1 I HOCH 1
HCOH
HCOH
I HCOH I
CHzOH Glucose
HC A
&
Alkali t -
I
HOCH
I I COH I COH
CHIOH
0
--
I
CH
I I HOCH , I HCOH I ' HCOH I HOCH
HCOH
1
Ethylene oxide form
,:'
CHtOH Ma"n0se
In the reactions relating to the exchanging of an aldebfde group for the end alcohol group (arrow 3) such as exists between d-aRrose and d-talose, the altrose is first oxidized to the di-basic acid. This loses water to produce the amyl-oxide ring structure. Upon reduction the mono-basic acid of talose is formed. This again loses water to form the amyl-oxide ring of talose and, upon reduction, the talose is produced but exists probably in the lactone form.
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The relationship between the aldoses and ketoses is shown by the arrows numbered 4. An example of this is the passing from glucose to fructose. To glucose is added phenyl-hydrazine forming the glucosozone which
11 1 HOCH I
I1 I HOCH I HCOH. I c-OH
C-H
HCOH
On
-+
I
HoC\;'
-HIO A
HCOH
HCOH
I HCOH I
HC
I HCOH I C--OH II
CHaOH
1
C-OH
la.
0 Di-basic acid
Amyl oxide form
CHZOH
1 I HCOH 1 HCOH I
HOCH HCOH Hs H+ HC
HCOH COH 1
I
COH
-HsO
+ *'
II
ll
0 Talonic acid
0
qf HCOH
,
II
0
Amy1 oxide form
CH?OH
CHIOH
I I
HOCH HCOH
HCOH Hs &
I HCOH I I
HCOH CH
I
0
upon hydrolysis and loss of water yields the glucozone. The glncozone upon reduction yields fructose (6). The double arrows between closely related optical isomers show that the change may he effected either way.
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OH
I
-
HOCH
Hydrolysis
I I
I I HC1
HCOH
HCOH
I I
HCOH I
HCOH CHzOH
C&OH
koH 'OH HOCH I
H&OH
I
HCOH
I
HOCH I
-2Hn0
I
HCOH I
HCOH CHIOH
I I
HOCH Hz
HCOH I
H~OH
I
CHsOH
CH20H
Conclusion In the presentation of the chart the author has incorporated into i t only the simpler structure of the carbohydrates and has left out the multiple forms possible if all the lactone structures were taken into consideration. According to Irvine (7) there are eleven possible structures for glucose alone; multiply the other homologs of this series by a proportional number of possible forms and i t is evident that the construction of a relationship chart showing all these structures would be practically impossible. Therefore, it is hoped that the presentation of the chart as i t is will facilitate the studying and teaching of the relationship among the simpler carbohydrates. More especially is it hoped that the chart may help to meet a need in the presentation of this phase of organic chemistry and that charts in general may come to have a greater part in the scientific studying and teaching of chemistry. Literature Cited J. Am. Chem. Soc., 28, 114 (1906). (1) ROSANOPI., ( 2 ) Ber., 24,2683 (1891); 27,3211 (1894). (3) HAWORTH. I.Chem. Soc., 1926,89-101; 1927,2436. (4) KIUANI, Ber., 20, 339 (1923). DE BRUYN and VANEKENSTBIN, Rec. trea. chim., 14, 204-16 (1895). (5) LOBRY "Outlines of Biochemistry," John Wiley & Sons, Inc., 1929, p. 505. ( 6 ) GORTNER, (7) IKVINE,"Progress in the Structural Study of Carhahydrates," Chenz. Reviews, 4, 203-29 (1927).
