LIGHT ABSORPTION STUDIES: PART XVI. THE ULTRAVIOLET ABSORPTION SPECTRA OF FLUOROBENZENES

1959 ◽  
Vol 37 (12) ◽  
pp. 1977-1985 ◽  
Author(s):  
W. F. Forbes
Keyword(s):  
Absorption Spectra ◽  
Light Absorption ◽  
Fluorine Atom ◽  
Ultraviolet Absorption ◽  
Mesomeric Effect ◽  
First Approximation ◽  
Absorption Studies

The ultraviolet absorption spectra of a series of fluorobenzenes are determined. It is found that as a first approximation a fluoro substituent does not appreciably affect the benzenoid absorption. The spectra are discussed on the assumption that the mesomeric effect of the fluorine atom is small.

LIGHT ABSORPTION STUDIES: PART XVII. THE ULTRAVIOLET ABSORPTION SPECTRA OF CHLOROBENZENES

1960 ◽  
Vol 38 (7) ◽  
pp. 1104-1112 ◽  
Author(s):  
W. F. Forbes
Keyword(s):  
Absorption Spectra ◽  
Chlorine Atom ◽  
Light Absorption ◽  
Fluorine Atom ◽  
Ultraviolet Absorption ◽  
Electronic Interaction ◽  
Mesomeric Effect ◽  
Spectral Changes ◽  
Absorption Studies ◽  
Solute Interactions

The ultraviolet absorption spectra of a series of chlorobenzenes are determined. The spectral data suggest that the apparent mesomeric effect of the chlorine atom is greater than that of the fluorine atom, that solvent–solute interactions are generally less important in chlorobenzenes than in fluorobenzenes, and that, as expected, the effective interference radius of the chlorine atom is large. Moreover, spectral changes in o-substituted chlorobenzenes are consistent with the assumption that maximum electronic interaction requires the chlorine atom to be in the same plane as the benzene ring. The conformations of o-chloroacetophenone and o-chlorophenol are briefly discussed.

LIGHT ABSORPTION STUDIES: PART XX. THE ULTRAVIOLET ABSORPTION SPECTRA AND INFRARED CARBONYL BANDS OF BENZOYL CHLORIDES

1961 ◽  
Vol 39 (12) ◽  
pp. 2452-2465 ◽  
Author(s):  
W. F. Forbes ◽  
J. J. J. Myron
Keyword(s):  
Absorption Spectra ◽  
Light Absorption ◽  
Ultraviolet Absorption ◽  
Mesomeric Effect ◽  
Intramolecular Vibration ◽  
Probable Explanation ◽  
First Approximation ◽  
Absorption Studies ◽  
Most Probable Explanation ◽  
Benzoyl Chlorides

The ultraviolet absorption spectra and infrared carbonyl bands of a number of substituted benzoyl chlorides are determined. It is found that as a first approximation the B-bands of the ultraviolet spectra are similar for benzoyl chlorides and for the corresponding benzaldehydes and acetophenones. The spectra are discussed in terms of previously stated hypotheses. In this way the order of the apparent negative mesomeric effect is deduced to be —NO2 > — COCl > —CHO > —COCH3, and the effective size of these substituents is confirmed to be in the order —NO2 > —COCH3 > —COCl > —CHO.The infrared carbonyl band occurs as a well-defined doublet in most of the ring-substituted benzoyl chlorides. The most probable explanation is that these doublets occur because of an intramolecular vibration.

LIGHT ABSORPTION STUDIES: PART XIX. THE ULTRAVIOLET ABSORPTION SPECTRA OF IODOBENZENES

1961 ◽  
Vol 39 (11) ◽  
pp. 2295-2305 ◽  
Author(s):  
W. F. Forbes
Keyword(s):  
Absorption Spectra ◽  
Light Absorption ◽  
Iodine Atom ◽  
Ultraviolet Absorption ◽  
The Other ◽  
Mesomeric Effect ◽  
Resonance Theory ◽  
Substituted Benzenes ◽  
Halogen Atoms ◽  
Absorption Studies

As a sequel to previous studies on the ultraviolet absorption spectra of halogen-substituted benzenes the spectra of iodobenzene in various solvents, and the spectra of a series of substituted iodobenzenes in cyclohexane solution, are reported. It is shown that these spectra can be rationalized qualitatively in terms of simple resonance theory, if the apparent mesomeric effect of the iodine atom is assumed to be greater for iodine than for the other halogen atoms.

LIGHT ABSORPTION STUDIES: PART XV. THE ULTRAVIOLET ABSORPTION SPECTRA OF ANISOLES

1959 ◽  
Vol 37 (8) ◽  
pp. 1305-1314 ◽  
Author(s):  
J. C. Dearden ◽  
W. F. Forbes
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Atom ◽  
Absorption Spectra ◽  
Hydroxy Group ◽  
Light Absorption ◽  
Spectral Properties ◽  
Ultraviolet Absorption ◽  
Steric Interactions ◽  
Absorption Studies ◽  
Methoxy Groups

Anisoles, compared with phenols, possess similar spectral properties, except that properties determined mainly by the hydrogen atom of the hydroxy group are modified. In this way, comparison of the ultraviolet absorption spectra of phenols and anisoles permits, for example, the study of the spectral effects of hydrogen bonding and the study of steric interactions involving the hydroxy and methoxy groups.

LIGHT ABSORPTION STUDIES: PART II. ULTRAVIOLET ABSORPTION SPECTRA OF SUBSTITUTED BENZOIC ACIDS AND PHENYL BENZOATES

1955 ◽  
Vol 33 (12) ◽  
pp. 1829-1839 ◽  
Author(s):  
W. F. Forbes ◽  
M. B. Sheratte
Keyword(s):  
Absorption Spectra ◽  
Light Absorption ◽  
Ultraviolet Absorption ◽  
Steric Effects ◽  
Benzoic Acids ◽  
Absorption Studies ◽  
Substituted Benzoic Acids ◽  
Electronic And Steric Effects

The spectra of a number of substituted benzoic acids, acetanilides, and phenyl benzoates are discussed in terms of the electronic and steric effects of substituents.

LIGHT ABSORPTION STUDIES: PART XII. ULTRAVIOLET ABSORPTION SPECTRA OF BENZALDEHYDES

1958 ◽  
Vol 36 (10) ◽  
pp. 1362-1370 ◽  
Author(s):  
J. C. Dearden ◽  
W. F. Forbes
Keyword(s):  
Absorption Spectra ◽  
Light Absorption ◽  
Electronic Spectra ◽  
Spectral Properties ◽  
Ultraviolet Absorption ◽  
Benzene Derivatives ◽  
Formyl Group ◽  
Steric Interactions ◽  
Absorption Studies ◽  
Acetyl Group

The electronic spectra of benzaldehydes in the region 220–360 mμ are recorded and discussed in terms of previously stated hypotheses. The formyl group is shown to endow benzene derivatives with spectral properties similar to those of the acetyl group in acetophenones, except that steric interactions are slightly modified.

LIGHT ABSORPTION STUDIES: PART XI ELECTRONIC ABSORPTION SPECTRA OF NITROBENZENES

1958 ◽  
Vol 36 (10) ◽  
pp. 1350-1361 ◽  
Author(s):  
W. F. Forbes
Keyword(s):  
Absorption Spectra ◽  
Electronic Absorption ◽  
Light Absorption ◽  
Electronic Absorption Spectra ◽  
Ultraviolet Absorption ◽  
Electronic Interactions ◽  
Absorption Studies

The spectra of nitrobenzenes are discussed in terms of previously proposed hypotheses relating electronic interactions and ultraviolet absorption spectra.

LIGHT ABSORPTION STUDIES: PART XVIII. THE ULTRAVIOLET ABSORPTION SPECTRA OF BROMOBENZENES

1961 ◽  
Vol 39 (5) ◽  
pp. 1131-1142 ◽  
Author(s):  
W. F. Forbes
Keyword(s):  
Spectral Data ◽  
Absorption Spectra ◽  
Light Absorption ◽  
Bromine Atom ◽  
Ultraviolet Absorption ◽  
Steric Effects ◽  
Benzene Derivative ◽  
Previous Part ◽  
Absorption Studies ◽  
Band Spectra

The ultraviolet absorption spectra of bromobenzene in various solvents, and the spectra of a series of substituted bromobenzenes in cyclohexane solution, are reported. The B-band spectral data confirm the hypotheses postulated for the B-band spectra of chlorobenzenes in the previous part of this series of papers. That is, the bromine atom usually gives rise to greater steric effects than the chlorine atom and the apparent mesomeric interaction as judged from these spectra increases with the size of the halogen substituent.Both bromobenzene and chlorobenzene C-band intensities are unusually small, and this is assumed to account for the frequent C-band similarity between the spectrum of a mono-substituted benzene derivative PhX, where X = OH, OCH3, NH2, and the spectrum of the corresponding chloro- or bromo-substituted PhX derivative.

LIGHT ABSORPTION STUDIES: PART XIV. THE ULTRAVIOLET ABSORPTION SPECTRA OF PHENOLS

1959 ◽  
Vol 37 (8) ◽  
pp. 1294-1304 ◽  
Author(s):  
J. C. Dearden ◽  
W. F. Forbes
Keyword(s):  
Hydrogen Bonding ◽  
Spectral Analysis ◽  
Absorption Spectra ◽  
Excited States ◽  
Light Absorption ◽  
Steric Effects ◽  
Benzene Derivatives ◽  
Substituted Phenols ◽  
Absorption Bands ◽  
Absorption Studies

A spectral analysis of benzene derivatives is extended to substituted phenols. The discussion emphasizes hydrogen bonding and steric effects which occur in phenols. Some of the phenolic absorption bands are ascribed to locally excited states.

LIGHT ABSORPTION STUDIES: PART V. THE RELATION OF MESOMERIC EFFECTS AND ULTRAVIOLET LIGHT ABSORPTION SPECTRA

1956 ◽  
Vol 34 (10) ◽  
pp. 1447-1456 ◽  
Author(s):  
W. F. Forbes ◽  
Audrey S. Ralph
Keyword(s):  
Absorption Spectra ◽  
Ultraviolet Light ◽  
Light Absorption ◽  
Absorption Data ◽  
Absorption Studies

A method for the determination of mesomeric effects from ultraviolet light absorption data is critically discussed. For halogen-substituted compounds, the method gives an order of mesomeric effects different from that which is usually accepted for the halogens.

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