Structural studies to investigate attractive interactions between nucleophiles and electron-deficient carbon atoms

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O'Leary, J., 2002. Structural studies to investigate attractive interactions between nucleophiles and electron-deficient carbon atoms. PhD, Nottingham Trent University.

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Abstract

This thesis is divided into five chapters. Chapter 1 gives an introduction to x-ray crystallography, detailing the experimental technique, structure solution and refinement. The use of x-ray crystallography to observe interactions in the fields of supramolecular chemistry and crystal engineering are discussed. The remainder of chapter 1 reviews the literature regarding intramolecular interactions between electron-rich and electron-deficient functional groups.

Chapters 2-5 form the results and discussion of the thesis. Chapter 2 details a reinterpretation of 1,5-interactions between dimethylamino or methoxy groups and sp2 carbon atoms in pen-naphthalene compounds 1. The pen-interactions of the methoxy group were found to be rather insensitive to the nature of the pen-substituent, hence are not attractive in nature, but are dominated be steric effects. The peri-interactions of the dimethylamino group decreases with peri group along the series: -CH=CHBr ~ -CONR2, -CH=C(COPh)2, -CO2H ~ CO2R, -COCH3, -CH=C(CN)CO2CH3, -CHO, - CH=C(CN)2, -CH=C(C(=O)O)2CMe2, this forms the relative order of through-space electron-attracting power for these groups. The nature of the N-C interactions are discussed and an equation (Equation 1) which can provide an indication as to whether the interactions are attractive or dominated by steric effects is introduced.

Chapter 3 is a report on the synthesis and structure of four 8-methylthio-l-alkenylnaphthalene compounds, where the alkene's terminal substituents are electron- withdrawing groups. There is a trend of decreasing S-C separation and out of plane deviations of the pen-substituents with increasing electron-attracting power of the alkene's terminal substituents: H, NO2 < CN, CO2Me < CN, CN < -C(C(=O)O)2CMe2. Equation 1 was modified to produce equation 2 in order to assess the nature of the S-C interactions, which appear to be dominated by steric effects.

Chapter 4 discusses 1,6-interactions between the dimethylamino group and sp2 carbon atoms of aldehydes and alkenes in 2,2'-disubstituted biphenyls. All structures show short N-C distances brought about by small inter-ring angles, which are unusual in such ortho-disubstituted biphenyls. Where the alkene's terminal substituents are a cyclic diketone 2 or are both cyano groups 3 the compounds have undergone intramolecular cyclisation to form zwitterions.

Chapter 5 concerns the synthesis and structure of the N-oxides and N,N'-dioxides of 3,3'-dinitro-2,2'-bipyridine and 5,5'-dimethyl-3,3'-dinitro-2,2'-bipyridine. All compounds show short contacts between nitro O atoms and the 2-C atoms of the distant pyridine ring. These interactions are controlled by the orientation of the nitro group with respect to the adjacent pyridine ring. There are also short contacts between oxide O atoms and nitro N atoms in three of the four structures. It is possible that the O-C and O-N interactions are in competition with each other.

Item Type:

Thesis

Creators:

O'Leary, J.

Date:

2002

ISBN:

9781369313833

Identifiers: