Alkanes IUPAC system

Simple alcohols are named by the IUPAC system as derivatives of the parent alkane, using the suffix -ol. 

The IUPAC rules assign names to unbranched alkanes as shown in Table 2.2. Methane, ethane, propane, and butane are retained for CH4, CH3CH3, CH3CH2CH3, and CH3CH2CH2CH3, respectively. Thereafter, the number of carbon atoms in the chain is specified by a Latin or Greek prefix preceding the suffix -ane, which identifies the compound as a member of the alkane family. Notice that the prefix n- is not part of the IUPAC system. The IUPAC name for CH3CH2CH2CH3 is butane, not n-butane. 

As you can see, cycloalkanes are named, under the IUPAC system, by adding the prefix cyclo- to the name of the unbranched alkane with the same number of carbons as the ring. Substituent groups are identified in the usual way. Their positions are specified by numbering the carbon atoms of the ring in the direction that gives the lowest number to the substituents at the first point of difference. 

Amines are named in two main ways in the IUPAC system, either as alkylamines or as alkanamines. When primary amines are named as alkylamines, the ending -amine is added to the name of the alkyl group that bears the nitrogen. When named as alkanamines, the alkyl group is named as an alkane and the -e ending replaced by -amine. 

When a hydrocarbon is substituted with other than alkyl groups a new problem arises, which can be illustrated by CH3CH2C1. This substance can be called either chloroethane or ethyl chloride, and both names are used in conversation and in print almost interchangeably. In the IUPAC system, halogens, nitro groups, and a few other monovalent groups are considered to be substituent groups on hydrocarbons and are named as haloalkanes, nitro-alkanes, and so on. 

By the IUPAC system, the suffix -ol for OH is added to the name of the parent hydrocarbon. N otice that alkane- + -ol becomes alkanol, with the e omitted ... 

The IUPAC system works consistently to name many different families of compounds. We will consider the naming of alkanes in detail, and later extend these rules to other kinds of compounds as we encounter them. The IUPAC system uses the longest chain of carbon atoms as the main chain, which is numbered to give the locations of side chains. Four rules govern this process. 

We have been using the common nomenclature of ethers, which is sometimes called the alkyl alkyl ether system. The IUPAC system, generally used with more complicated ethers, is sometimes called the alkoxy alkane system. Common names are almost always used for simple ethers. 

The IUPAC system for naming organic compounds is very logical and thorough. The rules for naming alkanes are the basis for naming the other organic compounds that you will study. Therefore it is important that you understand how to name alkanes. 

In naming alkyl halides by the IUPAC system, remember that a halogen is named as a substituent on an alkane. When numbering the alkyl halide, the halogens are numbered in the same way as alkyl groups and are cited alphabetically. 

The longest carbon chain containing the carbonyl group is selected and numbered starting with the carbon atom nearest the carbonyl group. If substitutents are present on the main chain, they are indicated by number of the carbon atoms to which they are attached. The number of the carbon atom of the carbonyl group is added to the front of the ketone. The IUPAC system replaces the -e of the name of the corresponding alkane by the suffix -one. 

Simple (symmetrical) ethers have the general formula R—O—R or Ar—O—Ar mixed (unsymmetrical) ethers are R—O—R or Ar—O—Ar or Ar—O—R. The derived system names R and Ar as separate words and adds the word ether. In the IUPAC system, ethers (ROR) are named as alkoxy- (RO-) substituted alkanes. Cyclic ethers have at least one O in a ring. 

The lUPAC system for naming alkanes is not difficuit to iearn, and the principies invoived are used in naming compounds in other famiiies as weii. For these reasons we begin our study of the iUPAC system with the ruies for naming aikanes and then study the ruies for aikyi haiides and aicohois. 

As organic chemistry developed, it became apparent that some systematic way of naming compounds was needed. About 70 years ago, the International Union of Pure and Applied Chemistry (IUPAC) devised a system that could be used for all organic compounds. To illustrate this system, we will show how it works with alkanes. 

A single alkane may have several different names a name may be a common name, or it may be a systematic name developed by a well-defined set of rules. The most widely used system is IUPAC nomenclature. Table 2.6 summarizes the rules for alkanes and cycloalkanes. Table 2.7 gives the rules for naming alkyl groups. 

Substitutive IUPAC nomenclature names epoxides as epoxy derivatives of alkanes. According to this system, ethylene oxide becomes epoxyethane, and propylene oxide becomes 1,2-epoxypropane. The prefix epoxy- always immediately precedes the alkane ending it is not listed in alphabetical order like other substituents. 

The International Union of Pure and Applied Chemistry (IUPAC) adopted a system that is clear. For noncyclic alkanes, the root gives the number of carbons in the longest chain. Each branch is described by a prefix indicating the number of carbons in the branch, and a number indicating the point of connection to the longest chain. (Numbering starts at the end of the chain which produces the smallest numerals.) The IUPAC names for the structures above are butane and 2-methyl propane. ... 

IUPAC rules allow for two systems of nomenclature, depending on the complexity of the acid molecule. Carboxylic acids that are derived from open-chain alkanes are systematically named by replacing the terminal -e of the corresponding alkane name with -oic acid.The carboxyl carbon atom is numbered Cl in this system. 

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