Proton chemically induced dynamic nuclear

The products observed in the reactions of Me2Ge with CCI3X (X = Cl, Br), PhCH2X (X = Br, 1), and Ph2CHCl, by proton chemically induced dynamic nuclear polarization ( H CIDNP) are those of net insertion of Me2Ge into the C—X bond and Me2Ge2X2 (X = Cl, Br) (Scheme 14.29). A two-step radical reaction takes place... 

For more complex spin systems, a computer program PHIP+ has been developed [13, 45] which allows the expected PHIP spectra to be calculated from the chemical shifts and coupling constants of the products. Depending upon which proton pair in the product molecule stems from p-H2, different - but characteristic - polarization patterns result [14]. The patterns also depend on the sign of the coupling constants. Simple sign rules governing the relative sequence of the emission and absorption lines in the PHIP spectra (i.e., their phase ) can be formulated in similar manner to the Kaptein Rules of chemically induced dynamic nuclear polarization (CIDNP) [15]. 

Palm and Dreeskamp (42,43) recently reported a CIDNP (Chemically Induced Dynamic Nuclear Polarization) study of the photolysis of a-(3,5-dimethoxyphenoxy)-acetophenone. From the polarization of the methylene protons they concluded that at least two of the products (diphenyl-1,4-butadione and a-(3,5-dimethoxy-4-hydroxyphenyl)-acetophenone) are formed from the singlet excited state. 

The direct proof that the Grignard formation reaction proceeds in this way was given by CIDNP (Chemical Induced Dynamic Nuclear Polarization) in 1972 by Bodewitz et al. [22,23]. They found the variation of peaks caused by the formation of the radical using CIDNP by measurement of the methylene proton in the Grignard formation reaction of CH3CH2I or (CH3)2CH2CH2Br. 

In 1969, Jemison and Morris followed the Stevens rearrangement of A, iV-dimethyl-4-nitrobenzylamine acetamide by NMR and noted a chemically induced dynamic nuclear polarization effect on benzylic protons consistent with a benzyl radical. They postulated that this Stevens-type rearrangement of a benzyl group from an ammonium center to a negatively-charged nitrogen center occurred via a homolytic dissociation... 

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