CIDNP Chemically induced dynamic polarizations

CIDNP chemically induced dynamic nuclear polarization... 

This mechanism is still quite controversial However, CIDNP (chemically induced dynamic nuclear polarization) experiments on a magnesium-dependent DNA-I polymerase (which hydrolyzes the P —O—P j linkage in a NTP in order to insert a new nucleoside in a growing DNA chain) being fed MgGTP revealed that GMP radical anions may indeed be involved . 

G. R. Lawler, Chemically Induced Dynamic Polarization (CIDNP). II. The Radical-Pair Model," Accfs. Chem. Res. 5, 25 (1972). 

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 technique most recently introduced to study radical cations is chemically induced dynamic polarization (CIDNP), a nuclear resonance method based on the observation of transient signals, substantially enhanced in either absorption or emission. These effects are induced as a result of magnetic interactions in radical or radical ion pairs on the nanosecond timescale. This method requires acquisition of an NMR spectrum during (or within a few seconds of) the generation of the radical ion pairs. The CIDNP technique is applied in solution, typically at room... 

Whereas NMR spectroscopy is generally applied to the diamagnetic allyl, pentadienyl, or cyclopentadienyl cations or anions, this technique is generally not applicable to the analogous radical species, although CIDNP (chemically induced dynamic nuclear polarization) has been observed for allyl140 and pentadienyl radical species139. More useful for the radicals, naturally, is EPR spectroscopy. 

Finally, it should be pointed out that methods used to study short-lived chemical intermediates in fast thermal reactions may be applicable also to photochemical studies. Radical intermediates, however generated, can be studied by CIDNP (chemically induced dynamic nuclear spin polarization), in which the n.m.r. spectrum of the reaction mixture is recorded during the reaction period. If a substrate is continuously irradiated with ultraviolet/visible light in the cavity of an n.m.r. spectrometer, the resulting n.m.r. spectrum ot the substrale/product mixture exhibits intensity variations as compared with the normal spectrum—intensity enhancement, reduction or even reversal (i.e. emission). Note that the spectrum involved is not... 

There is considerable agreement that the formation of Grignard reagents involves intermediate radicals. Evidence includes the trapping of intermediates by radical traps, CIDNP (chemically induced dynamic nuclear polarization) observations, and the occurrence of characteristic radical reactions (equation 6) such as disproportionation,... 

Abbreviations acac. Acetyl acetonate AIBN, 2,2-azobis(isobutyro) nitrile bae, dianion of A,iV -ethylenebis(acetylacetoneimine) bdhc, 1,19-dimethyl-AD-bisdehydrocorrinato bdm 1,3 pn, bis(l,3-diacetylmonoximeimino)propane bipy, bipyridyl Bz, Benzyl CIDNP, chemically induced dynamic nuclear polarization cod, cyclooctadienyl COD, cyclooctadiene Cp, Cp, ij-CsMes CT, charge transfer diphos, P(Ph)2CH2CH2P(Ph)2 dmgH,... 

CIDNP Chemically Induced Dynamic Nuclear Polarization... 

The altered NMR spectra characteristic of chemically induced dynamic polarization (CIDNP) (22) are observed during the photo-lytic decomposition of various peroxides in the presence of photosensitizers at ambient temperatures, as well as the thermal decomposition of these peroxides in the absence of light at temperatures where they have a short half-life. The reactions which are responsible for CIDNP are apparently similar in both cases. 

CIDNP (chemically induced dynamic nuclear polarization) Non-Boltzmann nuclear spin state distribution produced in thermal or photochemical reactions, usually from colligation and diffusion, or disproportionation of radical pairs, and detected by nuclear magnetic resonance spectroscopy by enhanced absorption or emission signals. 

Bargon, J., The Discovery of Chemically Induced Dynamic Polarization (CIDNP), Helv. Chim. Acta 2006, 89, 2082 2102. 

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