Die Lagerung der Atome im Raume

(The Arrangement of Atoms in Space)

J. H. van't Hoff (1874)

Translated by F. Herrmann

1877

pg. 11

 

Here van't Hoff considers the symmetrical formula:

CA(R1R2R3) CB(R4R5) CC(R4R5) CD(R1R2R3)

There are four asymmetric carbons (A, B, C, and D) and there are 24 = 16 possible isomers.

A
+
+
+
+
+
+
+
+
-
-
-
-
-
-
-
-
B
+
+
+
+
-
-
-
-
+
+
+
+
-
-
-
-
C
+
+
-
-
+
+
-
-
+
+
-
-
+
+
-
-
D
+
-
+
-
+
-
+
-
+
-
+
-
+
-
+
-

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

For carbon A he assigns: 8 +, 8 -.

For carbon B: 4 +, 4 -, 4 + , 4 -.

For carbon C: 2 +, 2-, 2+, 2-, 2 +, 2-, 2+, 2-

For carbon D: 8 x (1 +, 1 -)

 

Now van't Hoff considers the situation where A = D and B = C, as shown below:

A
+
+
+
+
+
+
+
+
-
-
-
-
-
-
-
-
B
+
+
+
+
-
-
-
-
+
+
+
+
-
-
-
-
B
+
+
-
-
+
+
-
-
+
+
-
-
+
+
-
-
A
+
-
+
-
+
-
+
-
+
-
+
-
+
-
+
-

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16


This situation creates a two fold-axis about between C2 and C3 or about AB . BA. Structures 1, 7, 10, and 16 are unique and are not accessible through any other structure. When structures 2,3,4,6,8, and 12 are rotated they become identical with 9, 5,13,11,15, and 14, respectively.



A
+
+
-
-
B
+
-
+
-
B
+
-
+
-
A
+
+
-
-

1
7
10
16


2
3
4
6
8
12

+
+
+
+
+
-
A
+
+
+
-
-
+
B
+
-
-
+
-
-
B
-
+
-
-
-
-
A

--------

----------

-----------

-----------

------------

-----------

-------------
-
+
-
-
-
-
A
+
-
-
+
-
-
B
+
+
+
-
-
+
B
+
+
+
+
+
-
A
9
5
13
11
15
14



This process creates 10 isomers, which he renumbered 1-10 as follows:

A
+
+
-
-
B
+
-
+
-
B
+
-
+
-
A
+
+
-
-

1
2
3
4

11
12
13
14
15
16

+
+
+
+
+
-
A
+
+
+
-
-
+
B
+
-
-
+
-
-
B
-
+
-
-
-
-
A

---

----

-----

-----

-----

----

----
-
+
-
-
-
-
A
+
-
-
+
-
-
B
+
+
+
-
-
+
B
+
+
+
+
+
-
A
5
6
7
8
9
10

Numbers 11-16 were not included by van't Hoff but they are included here as Fischer was to do eventually.

copyrighted F. E. Ziegler 2002