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 plane￾polarized light

Isomers are different compounds that have the same molecular formula. Constitutional isomers are isomers that differ because their atoms are connected in a different order. Stereoisomers differ only in arrangement of their atoms in space.Stereoisomers are not constitutional isomers. Enantiomers are stereoisomers whose molecules are nonsuperposable mirror images of each other. Diastereomer are stereoisomers whose molecules are not mirror images of each other

7.3 芳香烃的化学性质 Reactions of Aromatic Hydrocarbons 7.4 苯环上亲电取代的定位规律 Orientation of Reactions on Substituted Aromatic Rings

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

分离过程是将混合物分成组成互不相同的两种或几种产品的操作。 分离操作的作用：①为化学反应提供符合质量要求的原料，清除对反应或催化剂有害的 杂质，减少副反应和提高收率；②对反应产物起着分离提纯作用，以得到合格的产品，并使 未反应的反应物得以循环利用

Carbonyl compounds are a broad group of compounds that includes aldehydes, ketones,carboxylic acids, and esters

The primary source of alkanes is petroleum Natural gas consists chiefly of methane, but ethane, propane, butane, and isobutane are also present. Petroleum is a complex mixture of hydrocarbons that must be refined into different fraction before it can be used

The different arrangements of atoms caused by rotation about a single bond are called conformations (构象)of the molecule, and a specific conformation is called a conformer (构象异构体, conformation isomer). An analysis of the energy changes that a molecule undergoes as groups rotate about single bonds is called a conformational analysis (构象分析)

Cycloalkanes with only one ring are named by attaching the prefix cyclo- to the names of the alkanes possessing the same number of carbon atoms

Energy and the Relative Stability Kinetic energy is the energy an object has because of its motion. Potential energy is stored energy. It exists only when an attractive or repulsive force exists between objects