Achiral carbon

D1ASTEREOSELECTIVE ADDITIONS OF ACHIRAL CARBON NUCLEOPHILES TO CHIRAL 200... 

A review of the metal-catalysed ring opening of achiral epoxides by achiral carbon-, sulfur-, nitrogen- and halogen-containing nucleophiles and kinetic resolution of racemic epoxides has been published.24 The review also discusses the reactions of chiral bases with epoxides that give allylic alcohols. 

A carbon which is sp hybridized (tetrahedral structure) with four different substituents is called a chiral carbon. If the carbon doesn t have four different substituents or say at least the carbon has two of the same substituents, then it is an achiral carbon. 

DMAP is an efficient desynmetrisation catalyst. [Wilhs J Chem Soc, Perkin 1 1765 7999.] Thus it allows the use of an achiral or meso molecule, e.g. 3-substituted gjutaric anhydride to react with chiral alcohols e.g. 7 -l-(l -naphthyl)ethanol to produce (l 7 ,37 )-l(r-naphthyl)ethyl methyl 3-substituted-pentanoate di-esters (after treatment with diazomethane), which are now chiral at C-3. The achiral carbon atom at C-3 in the glutaric anhydride becomes chiral in the pentanoate (mono-ester of glutarate). [Theisen Heathcock J Org Chem 53 2374 1988, Theisen Heathcock J Org Chem 58 142 7995.]... 

Any reaction that creates a new bond to an achiral carbon has the potential to create a new chiral center if that carbon has a tetrahedral geometry in the product. Examples in which the starting carbon was also tetrahedral include free-radical halogenation (replace H- with X-) and a-alkylation of an enolate... 

Polarised micro-Raman spectra of aligned carbon SWNTs show that a distinction can be made between metallic and semiconducting SWNTs. The Raman band near 1580 cm is an intrinsic feature of metallic SWNTs. Calculations suggest that all achiral carbon SWNTs possess only eight Raman- and three IR-active modes. All chiral SWNTs were suggested to have fourteen Raman- and six IR-active modes. ... 

A more dramatic example of asymmetric synthesis is the photosynthetic process of plants which can convert solar energy into chemical energy with the assistance of chlorophyll molecules. In this complex process achiral carbon dioxide ends up as D-glucose. 

Identify chiral and achiral carbon atoms in an organic molecule. 

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