C-polarization

Robyr P, Gan Z and Suter U W 1998 Conformation of raoemo and meso dyads in glassy polystyrenes from C polarization-transfer NMR Macromolecules 31 8918- 23... 

Bashin A A and K Namboodiri 1987. A Simple Method for the Calculation of Hydration Enthalpies c Polar Molecules with Arbitrary Shapes. Journal of Physical Chemistry 91 6003-6012. 

Tabic 6-3. Vibrational assignment of the b- and c-polarized absorption spectra of T6 single crystal at 4.2 K. The proposed assignment is in agreement with the most intense vibrational modes found by Bimbaum et al. [64] in the excitation spectra of matrix isolated tetralhiophene (T4) at low temperature. 

While the origin is almost completely polarized along b, the c-polarized spectrum is twice as intense at lower energies starting at about 18000 cm-1 in conre-spondence with sharp c-polarized bands at (A) 18167, (B) 18084, and (C) 18026 cm-1. At the same energies the spectrum starts to show a broad background. 

Leachate Fractionation. Crude leachate was filtered through cartridge (Sep-Pak) in order to separate polar from nonpolar compounds. Nonpolar fraction was eluded from C. cartridge with acetone, evaporated under nitrogen gas and stored at -20 C. Polar leachate was lyophilized and stored at -20 C. 

Fig. 21. Calculated linear and 2D spectra for Ala -Ala-Ala using fi = 12.3 cm-1 and = 52°, which corresponds to an a-helical structure. Linear spectrum (a) and 2D scans for parallel (b) and perpendicular (c) polarizations of the pump and probe pulses. From Woutersen and Hamm (2001)./. Chem. Phys. 114, 2727-2737, 2001, Reprinted with permission from American Institute of Physics.

A different picture is observed when a polar radical reacts with a C—H bond of a polar molecule. For example, the reaction of an oxygen atom with the methane C—H bond is characterized by the activation energy of thermoneutral reaction /ic0 54.6 kJ mol-1 and parameter bre= 13.11 (kJ mol-1)172 while the reaction with the methanol C—H bond is characterized by Ed) 50 kJ mol-1 and parameter brc 12.55 (kJ mol-1)172 [30]. For these values of bre, the difference between the activation energies is 4.6 kJ mol-1. The decrease in the activation energy can be explained by the fact that the polar O—H group in the O H C—OH transition state interacts with the O H C polar reaction center. 

Fig. 39.3 LC PDA analysis, UV (297 nm) trace (using 1 mL/min gradient elution from 90% H20/MeCN (0.01% TFA) to MeCN (0.01% TFA) over 30 minutes followed by a 5 minute flush with MeCN on a Phenomenex Onyx CiglOO x 4.6mm column) showing a) non-polar, b) intermediate, c) polar fractions and d) characteristic absorbance profile of parotoid secretion from B. marinus.

FIGURE 4.34 Postulated mechanisms for MAO-catalyzed oxidation of primary amines, (A) SET (B) HAT mechanism, and (C) polar mechanism. 

Br—Cl covalent 2. O—H > S—O > H—Br > Cl—1 > N—Cl 3. property will tend to increase 4. cleavage ionic 4.2 1.(a) non-polar (b) polar (c) polar 3. both tetrahedral CH4 is non-polar and CH3OH is polar 4. less reactive since B and N now have octet in valence energy level 5. bent, polar... 

The comparably weak enhancement of the benzylic protons and the relatively strong C polarization for the benzylic carbons can be explained if the benzylic carbon adopts a pyramidal structure. Although radicals containing pyramidal carbon are relatively rare, the existing examples are derived from strained-ring... 

Fio. 21. Ehwtropic strengtha of water-methanol on three different columns with polar and apolar solutes. Tlie data were taken on a phenyl phase 0 -Bondapak. fiuty acids) with (a) polar and (b) apolar sohite. on Psitisfl OOS-2 with (c) polar and (d) apolar eluites. and on pyrocaibon witt (e) polar and (0 apolar solutes. Reprinted with permission fiom Colin and Ouiochon W). 

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