Out-of-plane parameters

I h e -M. l+ force field assigns default values for out of plane bending terms around an sp2 center. If a central atom has some out of plane parameters, then the first out of plane parameter involving th at cen tral atom is used if a specific parameter is n ot foiin d. 

TABLE 4. Selected statistical data for the absolute values of angular out-of-plane parameter, xNi (deg), and twist parameters, tni C2 and tc2 C3 (deg), together with pyramidality coefficients P (%) for the N1, C2 and C3 atoms of the enamine grouping both for a sample containing enamines with unrestricted substituents (size 474) and with carbon as the first atom in each of the RJ-R5 substituents (sample size 178)... 

TABLE 6. Torsion angles and out-of-plane parameters or crystalline 17-23 ... 

As in diatomic molecules the structure of greatest importance is the equilibrium structure, but one rotational constant can give, at most, only one structural parameter. In a non-linear but planar molecule the out-of-plane principal moment of inertia 4 is related to the other two by... 

Fig. 12 Dependence of the rate constant for alkaline hydrolysis for three amides [58] (x = 1, y = 2 x = 2, y = 1 and x = y = 2), and [59] on three different geometrical parameters the twist-torsional angle r (A), and the out-of-plane bending at the amide carbonyl (O) and nitrogen ( ) centres. [The geometrical...

Considerable changes are produced by the substituents in all the parameters involving the NH2 group the N—H distances increase markedly the H—N—H angles decrease toward the values for ammonium ion (109.5°) and for ammonia (106.7°), and the dihedral out-of-plane angles increase slightly (by 5° for p-nitroaniline[l-15N], but by very little... 

Pyranose Conformations. Figure 3 shows the different conformations for 6-membered rings (adapted from a drawing by Jeffrey and Yates (27)). There is a 9 parameter besides Q and ( > because several types of puckering are possible for a given Q and < ). In addition to the E (envelope) notation used in Figure 3, six-membered rings with only one out-of-plane atom are also called sofas or half-boats. The E descriptor was selected here because S is already used to denote skewed pyranose conformations (which have two atoms on opposite sides of the plane, separated by one atom). The H label is already used for half-chairs, which have two adjacent atoms on opposite sides of the mean plane. Typically, the E and H forms are not iiqportant unless a double bond is present. 

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