Newman projections definition

Figure 1.10 Definitions of the torsional angles fa ip, and w. These are all equal to 180° for a fully extended polypeptide chain (top left). to, defines rotation about the C,—Nl+1 bond. The normal tram planar peptide bond has = i/r = 180°, bottom) left, fa viewed along N —C bond (N >C) right, fa viewed along the C —C(C , — C j).

An alternative way of analyzing molecular shape, besides drawing a Newman projection, is to analyze the amount of twist about the bond that is necessary to cause some or all of the bonds from the near (upper) and far (lower) atoms to be totally eclipsed. This leads us to a definition of torsion angle. 

FIGURE 3. (a) 7>ans-folded structure of group 14 dimetallanes M2R4 (M = Si, Ge, Sn) with definition of the fold angle 0. (b) Newman projection along the M-M bond. The twist angle t=4... 

Figure 6.10. Inset Definition of M configuration of metal complexes, and generalized side view of an A/Af-metal carbene complex with the olefin approaching from the rear (equivalent to the Newman projection shown in a), (a) Favored approach, leading to the S,5-trans product, (b) Disfavored approach, leading to 5,/ -cis product, (cj Disfavored approach leading to the R,R trans product, (d) Disfavored approach leading to the R,S-ds product. After ref. [112],...

Give a definition of and illustrate examples of isotactic, syndiotactic, and atactic arrangement of macromolecules. This should include Fischer and Newman projections. 

Our main concern is conformation. As already mentioned in the Introduction, a dihedral angle along a a-bond is not restricted to a single value, but various energy minima are accessible (Fig. 2). For an easy visualization, we use the so-called Newman-projection. For the definition of the dihedral angle... 

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