21 April 1955

Dr. W. G. Schneider

Department of Theoretical Chemistry

Cambridge

England

Dear Dr. Schneider:

I have been interested to read your paper on the role of lone-pair electrons in the hydrogen bond, published in the January 1955 issue of the Journal of Chemical Physics.

Some of the arguments that you give and conclusions that you reach have already been stated in the literature. For example, in my book, THE NATURE OF THE CHEMICAL BOND, first edition, 1939, there is mentioned on page 269 that strong hydrogen bonds may involve an electron pair on each of the two bonded atoms. It is pointed out that this is indicated by the tetrahedral coordination in ice. You also mention this, in section 4 of your paper. The argument about ice and the use of the lone-pair electrons in determining the angles of hydrogen bonds is given again on page 28l of my book.

You also mention in section 4 of your paper that the hydrogen fluoride polymer is a striking example of a directed hydrogen bond. On page 278 of my book there is a statement that it is probable that the partial covalent character of the hydrogen bonds tends to stabilize bond angles of about 110° or 120° for fluorine.

On page 311 of my book there is a statement that in general the usual rules of stereochemistry (coplanarity for conjugated systems, tetrahedral values of bond angles) apply to both of the atoms connected by hydrogen bonds.

You may be interested, in connection with the introduction to your paper, also to read section 15d of my book, beginning on page 103 of the first edition. This section is on configurations for atoms with unshared electron pairs.

Sincerely yours,

Dictated by Linus Pauling

Signed in his absence:W