Anticlinal conformation

The analysis of these 25 compounds confirms the flexibility of dpg/dpg+. It can adopt a propeller like conformation and induce the formation of chiral crystals. It establishes predominantly two-dimensional H-bonding networks with the counter ion. From the perspective of the crystal engineer, an anticlinal conformation would maximize the non-linear properties of the molecule. However the non-linear optical response depends greatly on the molecular alignment. Non-centrosymmetric dispositions have not yet been achieved for dpg with an anti-anti conformation. The best strategy to attain NLO samples is by inducing a syn-anti conformation where a propeller structure might induce a chiral disposition of molecules and thus a non-centrosymmetric order. Another successful approach is to force crystallization with a chiral counterion. 

Draw the structure of raeso-tartaric acid (2,3-dihydroxybutanedioic acid) with an anticlinal conformation in a sawhorse projection. 

The synclinal and anticlinal conformations of 2-chloroethanol are chiral, which are designated as +sc and -sc, and +ac and -ac depending upon the direction of rotation. In addition, with the exception of the synperiplanar and antiperiplanar forms, all other conformations are chiral, i.e. there are an infinite number of chiral conformations. 

Figure 4 Five distinct structural conformers of Ll -dimethylferrocene (a) eclipsed synperiplanar conformer EO with 0 = 0° (b) eclipsed synperiplanar conformer E72 with (f> = 72° (c) staggered anticlinal conformer S108 with (p = 108° (d) eclipsed anticlinal conformer E144 with (p = 144° (e) staggered antiperiplanar conformer SI80 with 0 = 180°...

On the other hand, a computational study [159] of the Michael addition of propionaldehyde lithium enolate adding to E-crotonaldehyde indicates an anticlinal conformation around the forming bond (i.e. A eclipsing R2 in the ul topicity and A eclipsing H in the Ik topicity of Figure 5.9). 

The important conclusion drawn from this study (30) was that acetylcholine would most probably interact with muscarinic receptors in its less favored anticlinal conformation. The most active isomer, the (+)-f/ ans-enantiomer, of these cyclopropane analogues was found to have a torsion angle of 137° (anticlinal) between the ester oxygen and the quaternary nitrogen. This is significantly different from the 60° torsion angle in the synclinal conformation found by NMR and x-ray determinations to be the preferred conformation. 

The anticlinal conformation is higher in energy (by 16 kJ moP ) as a hydrogen atom and methyl group are forced extremely close to one another (0° separation). 

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