- Letter from LP to Dr. E. Rabinowitch, research Laboratory of Organic Chemistry, MIT. [Letters from Dr. E. Rabinowitch to LP February 2, 1940, and February 16, 1940] [Filed under LP Correspondence: #326.1]
February 9, 1940
Dr. E. Rabinowitch
Research Laboratory of Organic Chemistry
Massachusetts Institute of Technology
Dear Dr. Rabinowitch:
It is not possible to give a simple answer to the question you ask in your letter of February 7. The nitrogen atom in a porphine or phthalocyanine, whether bonded to carbon by two single bonds or a single bond and a double bond, would tend to form a bend to hydrogen in the median plane, as shown:
With single bonds to carbon the bond to hydrogen would rise above or fall below the CNC plane and with one CN double bond the NH bond would tend to be in the plane. There is, of course, not room for both hydrogen atoms in the molecule to lie in the plane of the molecule in these median positions, so that if the hydrogen atoms were to lie in the median planes one would be above and below the plane of the molecule, corresponding to your Figure 1.
In order to form hydrogen bonds, as in Figure 2, the hydrogen atoms would have to be pulled somewhat to one side from the expected bond directions. It is improbable that they would be pulled far enough out of line to lie between pairs of nitrogen atoms, because of the strain involved in the bond angles. On the other hand, the attraction of the other nitrogen atoms would, I think, pull the hydrogen atoms over somewhat to one side, giving weak hydrogen bonds. Each proton would be near to one nitrogen atom, at about 1.00 Å, and also would have one other nitrogen neighbor, at about 1.8 Å, I guess.
The protons would probably move occasionally from one nitrogen atom to another, but the frequency of this motion would be so low as not to influence the stability of the molecule.
You see that my position on the question is an intermediate one.
With best regards, I am
- Letter from LP to Dr. Edwin Cohn RE: Thanks him for the preprints and adds that he has no comments to add. [Letter from Cohn to LP January 23, 1940] [Filed under LP Correspondence: Box #66.10, file:(Cohn, Edwin, J. 1939-1940, 1942, 1944, 1947)]
- Letter from LP to L.A. Kimpton, Dean, Deep Springs, RE: Regrets that he has not yet found a suitable candidate for the position at Deep Springs. Invites Kimpton and his wife to have lunch at the Paulings' new house while in Pasadena. [Letters from Kimpton to LP January 25, 1940, February 15, 1940] [Filed under LP Correspondence: Box #198.9, file:(Kimpton, L. A.)]
- Letter from LP to Mr. H. B. van Wesep, Chief, Information Service, The Rockefeller Foundation, RE: Sends two additional photographs of the Crellin Laboratory. [Letter from LP to Mr. H. B. van Wesep January 31, 1940] [Filed under LP Correspondence: #427.2]
- Letter from LP to Mr. Joe Manildi, President, Tau Beta Pi RE: Nominates Mr. Edward Webster Crellin for honorary membership in Tau Beta Pi. [Filed under California Institute of Technology: Materials re: Division of Chemistry and Chemical Engineering, 1933-1963, No Date: Box #1.024, Folder 24.8]
- Letter from LP to Prof. L. H. Reyerson, University of Minnesota, RE: Describes Dr. Lawrence Brockway as having a good personality, strong work ethic, and capable of teaching both advanced courses and large, undergraduate classes. [Letter from L. H. Reyerson to LP February 1, 1940] [Filed under LP Correspondence: #340.5]
- Notes of Worker's Meeting of Pasadena Chapter of Federal Union. [Filed under AHP: Federal Union, Pasadena Chapter: Box # 5.007, Folder 7.4]
- Writes cheque to "Philharmonic Auditorium," $1.65. [Filed under LP Biographical: Business and Financial, Box 4.015, Folder 3]