Chemical shift, carbon coupling constants

The section on Spectroscopy has been retained but with some revisions and expansion. The section includes ultraviolet-visible spectroscopy, fluorescence, infrared and Raman spectroscopy, and X-ray spectrometry. Detection limits are listed for the elements when using flame emission, flame atomic absorption, electrothermal atomic absorption, argon induction coupled plasma, and flame atomic fluorescence. Nuclear magnetic resonance embraces tables for the nuclear properties of the elements, proton chemical shifts and coupling constants, and similar material for carbon-13, boron-11, nitrogen-15, fluorine-19, silicon-19, and phosphoms-31. 

Chemical shift and coupling constant data for carbons in the vicinity of fluorine substituents will be provided for the various classes of fluo-roorganic compounds discussed in the next four chapters. 

H and 13C NMR Data. The examples in Scheme 3.3 provide insight into expected proton and carbon chemical shift and coupling constant data for primary alkyl fluorides. It can be seen that the influence on both proton and carbon chemical shifts diminishes rapidly as one moves away from the site of fluorine substitution. 

H and13C NMR Data for Halofluoroalkanes. Scheme 3.13 provides some pertinent proton and carbon chemical shift and coupling constant data for fluorochloro- and fluorobromomethanes, whereas Scheme 3.14 contains relevant data for some typical halo fluoroalkanes. There does not appear to be anything unusual going on here. 

When the fluorine substituent is located at the 2-position or on any alkyl-substituted alkenyl carbon, it experiences the usual deshielding of 30-40 ppm (Scheme 3.38). Note the interesting variation in the chemical shifts and coupling constants for the 1-fluorocycloalkenes. 

H and13C NMR Data. The data given in Scheme 3.39 provide some guidelines for proton and carbon NMR chemical shift and coupling constant data for fluoroalkenes. Notice that in all cases, hydrogens that are cis to the fluorine substituent are deshielded relative to those that are trans. 

Proton and Carbon NMR Data. Some selected chemical shift and coupling constant data from proton and carbon spectra of chloro- and bromofluoroethylenes are presented in Scheme 3.46. 

Some typical proton and carbon chemical shift and coupling constant data for allylic and benzylic systems are given in Scheme 3.54. An alkenyl substituent or a phenyl substituent on either a CH2F or a —CHF- group has virtually no effect upon that carbon s chemical shift, and they also only affect the proton chemical shift by about 0.5 ppm. 

Carbon and Proton NMR Data. 13C and 11NMR chemical shift and coupling constant data for 2-fluoropyridine, 2-fluoroquino-lines, and 2-fluoroquinoxoline are provided in Scheme 3.62. 

Table II lists all pertinent chemical shifts and coupling constants for the known phosphinocarbenes and their respective diazo precursors. The (phosphino)(silyl)carbenes are all characterized by high field chemical shifts for phosphorus ( 24 to 50 ppm) and silicon (-3 to -21 ppm), and low field chemical shifts for carbon (120 to 143 ppm) with large couplings to phosphorus (147 to 203 Hz).

Table 8. Carbon Chemical Shifts and Coupling Constants in Annelated Benzenes ...

J-resolved two-dimensional carbon-13 NMR spectra [60, 61] separate chemical shifts and coupling constants in the two-dimensional JCH, <5C plane. Their practical value can be estimated on looking at Fig. 2.52. In the one-dimensional 13C NMR spectrum of... 

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