Some compounds often use common names according to their sources. It is necessary to master the structural formulas of the compounds represented by some common common common names, such as: lignol is a common name for methanol, alcohol (ethanol), glycol (ethylene glycol), glycerol (glycerol), carbolic acid (phenol), formic acid (formic acid), salicylaldehyde (o-hydroxybenzaldehyde), cinnamaldehyde (β-phenylacrolein) and cinnamaldehyde. 6- trinitrophenol), glycine (α-aminoacetic acid), alanine (α-aminopropionic acid), glutamic acid (α-glutaric acid), D- glucose, D- fructose (the open chain structure of sugar is expressed by Fisher projection), etc. There are also some compounds that commonly use its abbreviations and trade names, such as RNA (ribonucleic acid), DNA (deoxyribonucleic acid), aspirin (acetylsalicylic acid), coal phenol soap or lysol (47%-53% soapy water solution of three cresols), formalin (40% formaldehyde water solution), paracetamol (p-hydroxyacetanilide) and nicotine (nicotine). Common nomenclature Common nomenclature is also called customary nomenclature. It is required to master the meaning and usage of the prefixes "positive, different, new", "bo, zhong, Shu and Ji". Positive: stands for straight-chain alkane isomerism: refers to alkane with structure at one end of carbon chain. New: generally refers to alkane with structure at one end of carbon chain. B: A carbon atom connected to only one carbon is called a primary carbon atom. Para: The carbon atom connected with two carbons is called secondary carbon. Tertiary: The carbon atom connected with three carbons is called tertiary carbon. Quarter: The carbon atoms connected with four carbons are called quaternary carbon atoms. It is necessary to master the structure of common hydrocarbon groups, such as allyl, propenyl, n-propyl, isopropyl, isobutyl, tert-butyl and benzyl. Systematic nomenclature Systematic nomenclature is the key point of naming organic compounds, and we must master the naming principles of various compounds skillfully. Among them, the naming of hydrocarbons is the basis, while the naming of geometric isomers, optical isomers and multifunctional compounds is difficult and should be paid attention to. Keep in mind the "order rule" followed in naming. 1, the naming of alkanes The naming of alkanes is the basis for the naming of all open-chain hydrocarbons and their derivatives. Naming steps and principles: (1) Choose the longest carbon chain as the main chain, and when there are several identical carbon chains, choose the carbon chain containing substituent groups as the main chain. (2) When numbering the main chain, start from the end closest to the substituent. If there are several possible situations, each substituent should have as small a number as possible or the sum of substituent positions should be minimized. (3) Write the name to indicate the order of substituents with Arabic numerals, first write the order and name of substituents, and then write the name of alkanes; When there are multiple substituents, the simple ones come first and the complex ones come last, and the same substituents are combined and written, and the number of the same substituents is represented by Chinese characters and numbers; Arabic numerals and Chinese characters are separated by a half-word line. The memory formula is: choose the main chain and call it an alkane. Carbon position, fixed branch chain. Substituent: write in front, note the position, and connect with short lines. Different bases: simple to complex, same base, combined. 2. Naming of Geometric Isomers The naming of olefin geometric isomers includes cis, trans and Z and E methods. Simple compounds can be represented by cis-trans, and can also be represented by z and e. When expressed in cis-trans, the same atom or group on the same side of the double bond carbon atom is cis, and vice versa. If the four groups connected to the carbon atom of the double bond are not the same, they can only be represented by Z and E instead of cis-trans. According to the "order rule", the priority order of two pairs of groups is compared, and the two better groups are Z-type on the same side of the double bond carbon atom, and vice versa. It must be noted that cis, trans, Z and E are two different representations, and there is no necessary internal relationship. Some compounds can be represented by cis-trans, and they can also be represented by Z and E. The cis-trans is not necessarily Z-type, and the trans-trans is not necessarily E-type. For example, cis-trans isomers also exist in alicyclic compounds, and the two substituents are cis-trans on the same side of the ring plane, and vice versa. 3. Naming of optical isomers There are two ways to express the configuration of optical isomers: D, L and R, S. The D and L labeling method takes glyceraldehyde as the standard, which has certain limitations. It is difficult for some compounds to determine the corresponding relationship between them and the structure of glyceraldehyde. Therefore, more R and S labeling methods are used, which are labeled according to the spatial arrangement order of four different atoms or groups connected to chiral carbon atoms. Optical isomers are generally expressed by projection formula, so it is necessary to master the projection principle and configuration judgment method of Fisher projection formula. Judging the configuration according to the projection formula, it must be clear that in the projection formula, the groups connected by the horizontal lines are forward and the groups connected by the vertical lines are backward; Then, according to the "order rule", the priority order of the four groups connected by chiral carbon atoms is arranged, with the smallest group hydrogen atom as the top of a regular tetrahedron with carbon atoms as the center, and the other three groups as the corners of a triangle at the bottom of the regular tetrahedron. From the bottom of the tetrahedron to the top, the three groups are from large to small, with R clockwise and S counterclockwise. 4. Naming of bifunctional and multifunctional compounds The key to naming bifunctional and multifunctional compounds is to determine the matrix. The common situations are as follows: ① When halogen and nitro coexist with other functional groups, halogen and nitro are used as substituents, and other functional groups are the parent. ② When the double bond coexists with hydroxyl, carbonyl and carboxyl, alcohol, aldehyde, ketone and carboxylic acid are used as the matrix instead of olefin. ③ When hydroxyl group coexists with aldehyde group and carbonyl group, aldehyde and ketone are taken as the matrix. ④ When carbonyl and carboxyl coexist, carboxylic acid is taken as the matrix. ⑤ When double bonds and triple bonds coexist, the longest carbon chain containing both double bonds and triple bonds should be selected as the main chain, and the number of double bonds or triple bonds should be as low as possible. If the number of double bonds and triple bonds is the same, the double bonds should be given the lowest number.