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In organic chemistry, syn-and anti-addition are different ways in which substituent molecules can be added to an alkene (R 2 C=CR 2) or alkyne (RC≡CR). The concepts of syn and anti addition are used to characterize the different reactions of organic chemistry by reflecting the stereochemistry of the products in a reaction.
Although the syn vs. anti diastereomeric ratio ranges from mediocre to good (1.5:1 to 7.5:1), the substrate scope for such reactions remain rather limited, and the diastereoselectivity is found to be dependent on the stereogenic center on the amine starting material.
Anti-periplanar geometry will put a bonding orbital and an anti-bonding orbital approximately parallel to each other, or syn-periplanar. Figure 6 is another representation of 2-chloro-2,3-dimethylbutane (Figure 5), showing the C–H bonding orbital, σ C–H, and the C–Cl anti-bonding orbital, σ* C–Cl, syn-periplanar.
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The following reaction gives a syn:anti ratio of 80:20 using a lithium enolate compared to 97:3 using a bibutylboron enolate. Where the counterion determines stereoinduction strength, the enolate isomer determines its direction. E isomers give anti products and Z give syn: [21] Anti-aldol formation through E-enolate Syn-aldol formation through ...
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The syn-conformation shown above, with a dihedral angle of 60° is less stable than the anti-conformation with a dihedral angle of 180°. For macromolecular usage the symbols T, C, G +, G −, A + and A − are recommended (ap, sp, +sc, −sc, +ac and −ac respectively).
Howard spent four years at Kansas State, not winning the full-time starting job until last season, before choosing the Buckeyes over the NFL draft. “This has been a little different for us ...