Substituent groups, naming alkanes

Write the name of the compound The parent alkane is the last part of the name and is preceded by the names of the substituent groups and their numerical locations (locants) Hyphens separate the locants from the words... 

As you can see cycloalkanes are named under the lUPAC 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 m fhe usual way Their posifions are specified by numbering fhe carbon atoms of fhe ring m fhe direction fhaf gives fhe lowesf num ber to fhe subsfifuenfs af fhe firsf pomf of difference... 

Benzene derivatives. Tbe nomenclature is a combination of the lUPAC system and traditional names. Many of the derivatives are named by the substituent group appearing as the prefbt. These may be considered a subclass of the aliphatic-aromatic hydrocarbon family, which contains both aliphatic and aromatic units in its structures. Thus, alkylbenzenes are made up of a benzene ring and alkane units alkenylbenzenes are Composed of a benzene ring and alkene units and alkynylbenzenes comprise a benzene ring and alkyne units. Examples of alkylbenzenes include... 

You will modify this base name by adding the names of the branches (substituent group) in front of the base name. We name alkane branches by... 

This base name will be modified by adding the names of the branches (substituent groups) in front of the base name. Alkane branches are named by taking the name of the alkane that contains the same number of carbon atoms, dropping the — ane ending and adding —yl. Methane becomes methyl, propane becomes propyl, etc. If there is more than one branch, list them alphabetically. 

The substituent groups attached to the main chain are named by replacing the ending -ane of the alkane by -yl. We then have the alleyl groups... 

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. 

Most organic compounds can be derived from alkanes. In addition, many important parts of organic molecules contain one or more alkane groups, minus a hydrogen atom, bonded as substituents onto the basic organic molecule. As a consequence of these factors, the names of many organic compounds are based on alkanes. It is useful to know the names of some of the more common alkanes and substituent groups derived from them, as shown in Table 1.3. 

In cases in which the alkyl chain has more carbons than the ring, the compound is named as an alkane with the ring as a substituent group with a -yl suffix. 

There are five carbons in the longest alkyl chain, whereas the ring has only four carbons. Therefore, the ring is named as a substituent group on the alkane chain.)... 

In addition to the locations of the double bonds, another difference of alkenes is the molecule s inability to rotate at the double bond. With alkanes, when substituent groups attach to a carbon, the molecule can rotate around the C-C bonds in response to electron-electron repulsions. Because the double bond in the alkene is composed of both sigma and pi bonds, the molecule can t rotate around the double bond (see Chapter 6). What this means for alkenes is that the molecule can have different structural orientations around the double bond. These different orientations allow a new kind of isomerism, known as geometrical isomerism. When the non-hydrogen parts of the molecule are on the same side of the molecule, the term cis- is placed in front of the name. When the non-hydrogen parts are placed on opposite sides of the molecule, the term trans- is placed in front of the name. In the previous section, you saw that the alkane butane has only two isomers. Because of geometrical isomerism, butene has four isomers, shown in Figure 19.12. 

Cycloalkanes are named much like acyclic alkanes. Substituted cycloalkanes use the cycloalkane for the base name, with the alkyl groups named as substituents. If there is just one substituent, no numbering is needed. 

Name substituent groups as in alkanes, indicating their locations by the number of the main-chain carbon to which they are attached. The ethenyl group and the propenyl group are usually called the vinyl group and the allyl group, respectively. 

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. 

Each alkane-based substituent group branching from the parent chain is named for the straight-chain alkane having the same number of carbon atoms as the substituent. The ending -ane is replaced with the letters -yl, as shown in the following diagram. 

Other substituents are named as for alkanes, with a number specitying the location of the group and an appropriate prefix denoting how many groups of each kind are present. 

An alkyl group lacks one of the hydrogen substituents of an alkane. A methyl group (CH3—) is an alkyl group derived from methane (CH4). Unbranched alkyl groups in which the point of attachment is at the end of the chain are named in lUPAC nomenclature by replacing the -ane endings of Table 2.4 by -yl. 

Removing a hydrogen from an alkane results in an alkyl substituent (or an alkyl group). Alkyl substituents are named by replacing the ane ending of the alkane with yl. The letter R is used to indicate any alkyl group. 

Alkyl halides are named as alkanes with the halogen as a substituent, using the group names fluoro, chloro, bromo, and iodo. 

Branched chains and other groups are treated as in naming alkanes. Name the substituent group, and designate its position on the parent chain with a number. 

Structural isomerism in alkanes involves the formation of branched structures. Specific rules for systematically naming alkanes indicate the point of attachment of any substituent group, the length of the root chain, and so on. 

Substituents derived from alkanes by the removal of a hydrogen atom are called alkyl groups and are given the symbol R.The name of an alkyl group is formed by dropping the suffix -ane from the name of the parent alkane and adding -yl in its place. 

We form lUPAC names of alkenes by changing the -an- infix of the parent alkane to -en-(Section 3.5). Hence, CH2 = CH2 is named ethene, and CH3CH=CH2 is named propene. In higher alkenes, where isomers exist that differ in the location of the double bond, we use a numbering system. We number the longest carbon chain that contains the double bond in the direction that gives the carbon atoms of the double bond the lower set of numbers. We then use the number of the first carbon of the double bond to show its location. We name branched or substituted alkenes in a manner similar to the way we name alkanes (Section 3.3). We number the carbon atoms, locate the double bond, locate and name substituent groups, and name the main (parent) chain. 

In the lUPAC name of an ether, the parent alkane is named, and then the —OR group is named as an alkoxy substituent. Common names are derived by naming the two groups bonded to oxygen followed by the word "ether Ethers are weakly polar compounds. 

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