Citation
Hamilton, Walter Clark (1954) The crystal structure of dimethyl phosphinoborine trimer. The method of least squares in electron diffraction. Some structural studies by the electron diffraction by gas molecules. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd12152003090535
Abstract
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The crystal structure of dimethyl phosphinoborine trimer, [(CH[subscript 3][subscript 2]PBH[subscript 2][subscript 3], has been determined by analysis of its xray diffraction maxima. Use was made of a threedimensional Patterson function, least squares on the structure factors, and a threedimensional electrondensity difference map. The space group is P[subscript nma]; the unit cell constants are a = 11.16 [angstroms], b = 13.16 [angstroms], and c = 10.53 [angstroms]. There are four molecules per unit cell. The molecule has a cyclohexanelike ring of alternating phosphorus and boron atoms, with two methyl groups attached to each phosphorus atom. It has a plane of symmetry, and the environment of each phosphorus atom is C[subscript 2v]. The following average structural parameters were found: [...].ome attention is given to the determination of temperature factors from the difference map and to fitting of atomic form factors by Gaussians. The R factor for the final structure is 0.169.
The advantages of the method of least squares, as contrasted to the usual correlation treatment, in electron diffraction investigations of molecular structure are outlined. Special attention is given to visual data and to the weighting of observations, including remarks on the use of a nondiagonal weight matrix and the derivation of weights from the goodness of fit, and to obtaining reliable estimates of error, and of error correlation, for the parameters.
The method of least squares has been applied to electron diffraction photographs of bicycloheptadiene, C[subscript 7]H[subscript 8], and bicyclooctane, C[subscript 8]H[subscript 14]. In the case of bicyeloheptadiene, a simple valenceforce potential function adequately explains the values found for the structuralparameters. The structure of difluoromethane has been reinvestigated by electron diffraction.
Item Type:  Thesis (Dissertation (Ph.D.)) 

Degree Grantor:  California Institute of Technology 
Division:  Chemistry and Chemical Engineering 
Major Option:  Chemistry 
Thesis Availability:  Public (worldwide access) 
Research Advisor(s): 

Thesis Committee: 

Defense Date:  1 January 1954 
Record Number:  CaltechETD:etd12152003090535 
Persistent URL:  http://resolver.caltech.edu/CaltechETD:etd12152003090535 
Default Usage Policy:  No commercial reproduction, distribution, display or performance rights in this work are provided. 
ID Code:  5000 
Collection:  CaltechTHESIS 
Deposited By:  Imported from ETDdb 
Deposited On:  17 Dec 2003 
Last Modified:  26 Dec 2012 03:13 
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