1,2-Dimethylenecyclobutane<sup>1,2</sup>

Blomquist, A. T.; Verdol, Joseph A.

doi:10.1021/ja01612a026

Cited by 67 publications

(12 citation statements)

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“…It is difficult to see why this should be so, as the bonds must be coplanar. The corresponding 1,2-dimethylenecyclobutane [13], in contrast, does show a significant fall in frequency (to 1626 cm -1) as compared with the mono-methylene derivative (1678 cm -1). But in tetramethylencyclobutane the frequency again rises to 1662 cm -1 [96].…”

Section: Conjugation Effects In Ringsmentioning

confidence: 85%

Alkenes and Vibrations of C=N and N=N Links

Bellamy¹

1980

The Infrared Spectra of Complex Molecules

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A good deal of new data has accumulated on the positions of C=C absorptions in different chemical environments, so that we are now in a better position to discuss the various factors which control the frequency shifts. But it is clear that, in this instance, both chemical and physical factors are important, and much remains to be done to determine the relative impacts of each. These two factors can be simply defined as follows. Chemical effects arise from alterations in the electron distribution within the bond which follow the replacement of one substituent by another. There is therefore a change in bond character which is reflected in an altered force constant and a shift in the vibrational frequency. However, the vibrational frequency can also be affected by factors such as substituent mass, bond-angle changes and vibrational coupling. These are purely physical effects, and they do not correspond to any change in the force constant of the bond, except insofar as angle changes may affect the hybridization. In many situations both types of effect are in operation. In conjugated systems, for example, the force constant of the bond is lowered as compared with the non-conjugated case, due to the delocalization of the 7t electrons. This leads to a shift to lower frequencit:s. However, there is now an increased possibility of vibrational coupling between the two C=C links, which will modify the frequency, although in itself it does not alter the force constants.Some of the most informative studies in this field have been those concerned with the effects of bond-angle changes and of ring strain, and these will therefore be considered first, as they illustrate very well the substantial impact of physical effects, and the difficulties which arise in disentangling them from the chemical effects which occur simultaneously.

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Section: Conjugation Effects In Ringsmentioning

confidence: 85%

Alkenes and Vibrations of C=N and N=N Links

Bellamy¹

1980

The Infrared Spectra of Complex Molecules

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“…For the synthesis of 1,2-dimethyIidenecyclobutane (6e), commercial lrans-cyclobutane-1,2-dicarbonyl chloride (9) was converted to the diamine by reaction with Me2NH [18] and LiAIH4 [19]. The diamine was oxidized to the di-N-oxide and pyrolyzed 1161 to furnish diene 6d 1171 [20]').…”

Section: 'mentioning

confidence: 99%

“…2J(C,F) = 13.3, *J(C,F) = 9.6); 30.6 (dd, 'J(C,F) = 3.4, 'J(C,F) = 1.7); 135.2 (d, 4J(C,F) = 3.1); 29.9. 19F-NMR: Table I (20), 51 (67). 1 0 a e -I,l-D~fluoro-3,4-dirne/hyl-l H-cyclopropuhenzene (4a).…”

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