Before 1951 only relative configurations of chiral molecules were known. Configurations of chiral molecules were related to each other through reactions of known stereochemistry. The standard compound was glyceraldehyde
An equimolar mixture of two enantiomers is called a racemic form (either a racemate or a racemic mixture). A racemic form shows no rotation of planepolarized light
More environment-friendly methods Natural insect attractants — instead pesticide Less reactive compounds organic refrigerants and aerosol propellant — instead Freon (that destroy the Earth’s ozone layer) Cars with more efficient combustion engines — reduce the massive amount of automobile
Aldehydes are named by replacing the terminal –e of the corresponding alkane name with –al. The longest chain selected as the base name must contain the –CHO group, and the –CHO carbon is always numbered as carbon 1
More reactive than benzene toward electrophilic substitution NO2 An deactivating group Less reactive than benzene toward electrophilic substitution Ortho-para director Meta director
7.1 芳香烃的分类 结构及命名 Classification, Structures and Nomenclature of Aromatic Compounds 7.2 芳香烃的来源及物理性质 Sources and Physical Properties of Aromatic Hydrocarbons
The most characteristic reactions of benzenoid arenes are the substitution reactions that occur when they react with electrophilic reagents. The electrophiles are either a positive ion (E+) or some other electron-deficient species with a large partial positive charge
