Ethane angle

The force-field model for ethanol contains C-O and O—H bond-stretching contributions in ethane thiol these are replaced by C—S and S—H parameters. Similarly, in ethanol there will be angle-bending terms due to C—O—H, C—C—O and H—C—O angles in ethane thiol these will be C—S—H, C—C—S and H—C—S. The torsional contribution will be modified appropriately, as will the van der Waals and electrostatic interactions (both those within the... 

FIGURE 8.1 Z-matrix for ethane. The first column is the element, the second column the atom to which the length refers, the third column the length, the fourth column the atom to which the angle refers, the fifth column the angle, the sixth column the atom to which the confonnation angle refers, and the seventh column the confonnation angle. 

Practice working with your Learning By Modeling software Construct molecular models of ethane ethylene and acetylene and compare them with respect to their geometry bond angles and C—H and C—C bond distances... 

The structural features of methane ethane and propane are summarrzed rn Ergure 2 7 All of the carbon atoms have four bonds all of the bonds are srngle bonds and the bond angles are close to tetrahedral In the next sectron we 11 see how to adapt the valence bond model to accommodate the observed structures... 

FIGURE 2 7 Structures of methane ethane and propane showing bond distances and bond angles... 

Bonding m n butane and isobutane continues the theme begun with methane ethane and propane All of the carbon atoms are sp hybridized all of the bonds are ct bonds and the bond angles at carbon are close to tetrahedral This generalization holds for all alkanes regardless of the number of carbons they have... 

The structural feature that Figures 3 2 and 3 3 illustrate is the spatial relationship between atoms on adjacent carbons Each H—C—C—H unit m ethane is characterized by a torsion angle or dihedral angle which is the angle between the H—C—C plane... 

Conformations m which the torsion angles between adjacent bonds are other than 60° are said to have torsional strain Eclipsed bonds produce the most torsional strain staggered bonds none Because three pairs of eclipsed bonds are responsible for 12 kJ/mol (2 9 kcal/mol) of torsional strain m ethane it is reasonable to assign an energy cost of 4 kJ/mol (1 kcal/mol) to each pair In this chapter we 11 learn of additional sources of strain m molecules which together with torsional strain comprise steric strain... 

Bond Distances, Bond Angles, and Bond Energies in Ethane, Ethene, and Ethyne (Table 9 1, p 342) Stmctures of a-Ammo Acids (Table 27 1, pp 1054-1055)... 

All bonds between equal atoms are given zero values. Because of their symmetry, methane and ethane molecules are nonpolar. The principle of bond moments thus requires that the CH3 group moment equal one H—C moment. Hence the substitution of any aliphatic H by CH3 does not alter the dipole moment, and all saturated hydrocarbons have zero moments as long as the tetrahedral angles are maintained. 

The formalism that we have set up to describe chain flexibility readily lends itself to the problem of hindered rotation. Figure 1.8a shows a sawhorse representation of an ethane molecule in which the angle of rotation around the bond is designated by electron repulsion between the atoms bonded to... 

Sketch the form of the potential energy as a function of torsional angle cj) for the torsional vibration in (a) ethane, (b) CH3NO2, (c) 2-fluorophenol, (d) CH2FOH, and... 

Structure. Ethylene is a planar molecule with a carbon—carbon bond distance of 0.134 nm, which is shorter than the C—C bond length of 0.153 nm found in ethane. The C—H bond distance is 0.110 nm, and the bond angles are [Pg.432]

The torsional strain is a sinusoidal function of the torsion angle. Torsional strain results from the barrier to rotation about single bonds as described for ethane on p. 56. For molecules with a threefold barrier such as ethane, the form of the torsional barrier is... 

Fig. 3.1. Potential energy as a function of torsion angle for ethane.

A completely different structural motif has very recently been found in the red-brown phosphide CasPg, formed by direct fusion of Ca metal and red P in the correct atom ratio in a corundum crucible at 1000 C. The structure comprises Ca + cations and Pg anions, the latter adopting a staggered ethane conformation. (Note that P+ is isolobal with C and P with H so that C2H6 = [(P+)2(P"")6] = Ps - -) The internal P-P distance is 230.1pm and the terminal P-P distances 214.9-216.9 pm, while the internal PPP angles are 104.2-106.4° and the outer angles are 103.4-103.7°. 

Step through the sequence of structures depicting bond rotation in ethane. Plot energy (vertical axis) vs. HCCP torsion angle (horizontal axis). Do the minima correspond to staggered structures Do the maxima correspond tc eclipsed structures If not, to what do they correspond ... 

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