Hydrogen ortho

Phenyllithium caimot be formed from fluoroben2ene. Instead, the electronegativity of fluorine makes the ortho hydrogen sufficiently acidic to permit reaction with / -butyUithium in tetrahydrofuran at —50°C to give 2-fluorophenyllithium [348-53-8]. An isomer, 4-fluoropheny11ithium [1493-23-8] was reported to be explosive in the soHd state (167). 

The ortho hydrogen atoms surrounding the central carbon atom show considerable steric overlap. Therefore, it can be assumed that the three aryl groups in the dye are not coplanar, but are twisted in such a fashion that the shape of the dye resembles that of a three-bladed propeller (9). Substitution in the para position of the three aryl groups determines the hue of the dye. When only one amino group is present, as in fuchsoriimine hydrochloride [84215-84-9] = 440 nm (2), the shade is a weak orange-yeUow. 

When one of the ortho hydrogens is replaced by deuterium, the rate drops from 1.53 X 10 " s to 1.38 X lO s. What is the kinetic isotope effect The product from such a reaction contains 60% of the original deuterium. Give a mechanism for this reaction that is consistent with both the kinetic isotope effect and the deuterium retention data. 

There are, however, short Rh—H contacts (2.77-2.84A) to ortho-hydrogens in phenyl groups. The Rh—P bond trans to Cl is some 0.1 A shorter than the others, evidence of the weak trans-influence of chloride [46]. 

The range of observations concerning the direct comparison of the catalytic activity of nickel and rich in nickel alloys with their respective hydride phases has been further extended on reactions of a more complicated nature such as para-ortho hydrogen conversion and ethylene hydrogenation. 

The conversion of ortho-hydrogen to para-hydrogen is slow in the absence of a catalyst. Therefore, as one cools room-temperature hydrogen to low temperatures, the ortho. para ratio remains at 3 1, and entropy is present that results from the mixing of these two different types of hydrogen. 

Catalysts such as charcoal can be used to maintain the equilibrium ratio of ortho-hydrogen to para-hydrogen with decreasing temperature.1 When this happens, heat capacity measurements give the equilibrium value for the entropy of hydrogen. 

In such cases, the more acidic hydrogen is removed. Since acidity is related to the field effect of Z, it can be stated that an electron-attracting Z favors removal of the ortho hydrogen while an electron-donating Z favors removal of the para hydrogen. The second factor is that the aryne, once formed, can be attacked at two positions. The favored position for nucleophilic attack is the one that leads to the more stable carbanion intermediate, and this in turn also... 

In Table 5 are summarized theoretical lower-excitation energies and corresponding intensities for nonalternant hydrocarbons for which experimental data are available. Theoretical values are in general agreement with experimental ones. The predicted excitation energies for heptalene (VII) are rather small as compared with experimental data. This may arise as a consequence of nonplanarity due to the steric repulsions between ortho-hydrogen atoms. 

The Sm-N distances are consistent with single a bonds suggesting the presence of a (C H NNC.H dianion. However, the 1.25(1) a NN distance is the same" as tire N=N double bond distances in a variety of azobenzene structures. The molecule also contains distorted N-C (phenyl) distances, which are stretched from a normal 1.42 8 distance to 1.56-1.61 8. In addition, the samarium atoms are displaced asymmetrically such that both come within 2.29-2.34 8 of the ortho hydrogens of a single phenyl ring in a bonafide agostic (6<0 Sm-H interaction. The ability of Sm(II) to structurally distort azobenzene in this way is remarkable. 

Other transformations supplied by these enzymes are para-ortho-hydrogen conversion, and the exchange reaction between H2 and protons of water.409-412 The hydrogenase enzymes found in various microorganisms are very different in their protein structure and in the types of electron carrier they use. 

A liquid with a high ortho hydrogen concentration evaporates even without any external input of power. 

The effects of an uncompensated electron are (1) to split the molecule s spectral lines into doublets, or in the case of certain diradicals, into triplets, (2) to make the molecule paramagnetic, (3) to catalyze the conversion of para and ortho hydrogen molecules, and (4) to cause paramagnetic resonance absorption. 

Although the resonance or delocalization stabilization of tri-phenylmethyl will be at its maximum only when the radical is completely planar, such a structure involves repulsion by adjacent ortho hydrogen atoms ... 

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