Alkanes with Substituents

Write the lUPAC names for alkanes with substituents and draw their condensed structural formulas and skeletal formulas. 

FIGURE 11.3 The stmctural isomers of C4H10 have the same number and type of atoms but are bonded in a different order. What makes these molecules stmctural isomers  

In another example, we can draw the condensed structural formulas for three different structural isomers with the molecular formula C5H12 as follows  

Identify each pair of formnlas as structural isomers or the same molecule. CH3 CH3 

Why does the following formula represent a different structural isomer of the molecules 

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In Summary Four rules should be applied in sequence when naming a branched alkane (1) Find the longest chain (2) And the names of aU the alkyl groups attached to the ston (3) number the chain (4) name the alkane, with substituent names in alphabetical order and preceded by numbers to indicate their locations. Haloalkanes are named in accord with the rules that apply to naming the alkanes, the halo substituent being treated the same as alkyl groups. 

Chapter 11 has a new order of topics 11.1 Organic Compounds, 11.2 Alkanes, 11.3 Alkanes with Substituents, 11.4 Properties of Alkanes, 11.5 Alkenes and Alkynes, 11.6 Cis-Trans Isomers, 11.7 Addition Reactions, and 11.8 Aromatic Compounds. 

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... 

Branched-chain alkanes, also known as isoparaffins or isoalkanes, are possible when n > 4. The prefix iso is used when two methyl groups are attached to a terminal carbon atom of an otherwise straight chain and the prefix neo when three methyl groups are attached in that manner. Branched-chain alkanes are sometimes regarded as normal alkanes with attached substituent alkyl groups. An example is... 

Hall process (Hall-Herault process) The production of aluminum by the electrolysis of aluminum oxide dissolved in molten cryolite, haloalkane An alkane with a halogen substituent. 

The nomenclature of cycloalkanes is almost the same as that for alkanes, with the exception that the prefix cyclo- is to be added to the name of the alkane. When a substituent is present on the ring, the name of the substituent is added as a prefix to the name of the cycloalkane. No number is required for rings with only one substituent. 

Tribromo acids of this type (41) can also be used for the synthesis of quinolizidine and other 1-azabicyclic alkanes with functional substituents. 

Table 2.9.2 presents some of the halogenated hydrocarbons that can be effectively extracted out from aqueous and nonaqueous matrices by liquid-liquid or other nonpurge and trap extraction. Such compounds include di-, tri-, tetra-, penta-, and hexahalo- substituents aromatics and cyclohexanes, and haloderiva-tives of alkanes with carbon number greater than 6. Characteristic mass ions for GC/MS identification are also presented for some of these listed compounds. 

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. 

When several substituents are present on a benzene ring, the ring is numbered in the same manner as the rings of cycloalkanes—that is, so that the numbers for the substituents are as low as possible. In addition, some special terms are used with disuhsti-tuted benzenes only. Two substituents on adjacent carbons (positions I and 2) are said to be ortho, or o-. Two substituents on positions 1 and 3 are meta, or m-. And two substituents on positions 1 and 4 are para, or p-. Finally, if an alkyl group with six or more carbons is attached to a benzene ring, the compound is named as an alkane with a phenyl substituent. Some examples are as follows ... 

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. 

Haloalkanes can be named just like alkanes, with the halogen atom treated as a substituent. Halogen substituents are named fluoro-, chloro-, bromo-, and iodo-. 

An alkane with all its carbon atoms in a single chain, with no branching or alkyl substituents, (p. 88)... 

There are two ways of naming alkyl halides. The systematic (IUPAC) nomenclature treats an alkyl halide as an alkane with a halo- substituent Fluorine is fluoro-, chlorine is chloro-, bromine is bromo-, and iodine is iodo-. The result is a systematic haloalkane name, as in 1-chlorobutane or 2-bromopropane. Common or trivial names are constructed by naming the alkyl group and then the halide, as in isopropyl bromide. This is the origin of the term alkyl halide. Common names are useful only for simple alkyl halides, such as the following ... 

The nomenclature of alkenes and alkynes follows the same rules as alkanes, except the double or triple bond must be numbered. The multiple bond is numbered on the first number to which it is assigned. Also, because double bonds have a rigid configuration, they can exhibit a cis or trans isomerism. A cis structure is one with substituents on the same side of the double bond, and the trans is one with the substituents are on opposite sides of the double bond. 

So far, only the mercury-photosensitized chemistry, discussed above, allows direct functionalization of alkanes with a Si substituent under mild conditions (equation 36). ... 

An alkyl halide is named as an alkane with a halogen substituent— that is, as a halo alkane. To name a halogen substituent, change the -ine ending of the name of the halogen to the suffix -o (chlorine chloro). 

Name the parent chain as an alkane, with the halogen as a substituent bonded to the longest chain. 

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