Alkyl and Halogen Substituents

If there is no third branch, begin numbering nearest the substituent whose name has alphabetic priority  

Write the name as one word, placing substituents in alphabetic order and using proper punctuation. 

PROBLEM 2.3 Give an lUPAC name for the following compounds a. CH3CHCH2CH3 b. GH3CH2CHCH3 c. CH3 

As illustrated for the methyl group, alkyl substituents are named by changing the -ane ending of alkanes to -yl. Thus the two-carbon alkyl group is called the ethyl group, from ethane. 

The two-carbon alkyl group is the ethyl group. The propyl group and the isopropyl group are three-carbon groups attached to the main chain by the first and second carbons, respectiveiy. 

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The equilibrium concentrations of many disubstituted benzenes (containing alkyl and halogen substituents) show that the meta isomer is in nearly all cases the most thermodynamically stable. It is not obvious why this should be so. Shine182 had discussed this problem in terms of the relative sizes of the standard enthalpy and entropy changes between any pair of isomers. 

This difference is clearly shown by the p/CTS values plotted in Fig. 4, which are calculated from the extensive data for ester cleavage by /3-CD (Tables A5.2 and A5.3) accumulated by Fujita and coworkers (Matsui et al., 1985 Fujita, 1988). For m-alkyl and halogen substituents there is a good... 

Simple benzene derivatives show most of the characteristics of benzene, including the moderate band in the 210-nm region and the benzenoid band in the 260-nm region. Alkyl and halogen substituents increase the values of Amax by about 5 nm, as shown by the examples in Table 16-2. An additional conjugated double bond can increase the value of Amax by about 30 nm, as shown by the UV spectrum of styrene in Figure 16-19. 

The example shows a sequential approach to the study of discrete variations. The Willgerodt-Kindler reaction was studied with a set of para substituted acetophenones, see Schema 9. As the reaction failed with strong electron-withdrawing substituents, the study was limited to include donor, alkyl, and halogen substituents. 

Hydroxyl groups take precedence over ( outrank ) alkyl groups and halogen substituents m determining the direction m which a carbon chain is numbered The OH group is assumed to be attached to C 1 of a cyclic alcohol and is not numbered... 

The Bergmann variation of the Balz Schiemann reaction is a two-step process featuring copper- or copper halide-catalyzed decomposition of aqueous or acetone solutions of arenediazonium fluoroborates containing alkyl or halogen substituents [30] A recent modification is a one-step technique featuring simultaneous diazoti-zation and decomposition by addition of aqueous sodium nitrite at 25 °C to a mixture of fluorobonc acid, copper powder, and 2 isopropyl 6 methylaniline to give 2-isopropyl-6 methylfluorobenzene in 73% yield [37]... 

The thermal isomerization of dihalocyclopropanes is facilitated by the presence of aryl, alkyl and alkoxy substituents in the three-membered ring. Phenyl substituted systems may give rise to indenes, and in the alkyl series the dehydro-halogenation of 2,3-dihalocyclopropane derivatives may lead to dienes. 

In an endeavor to study the transmission of substituent effects in imidazoles Noyce (73JOC3762) examined the solvolysis rates of a series of l-(l-methylimidazolyl)ethyl p-nitrobenzoates (75-77 OPNB = p-nitrobenzoate). The relative rates (75 76 77 = 1 13 15) parallel the relative electron densities in 1-methylimidazole as deduced from chemical shift data. By comparison with other heteroarylethyl p-nitrobenzoates the effective replacement constants, crXr, were determined as a-2-im = —0.82, o-J-im = —1.01 and <7-5.1 = —1.02. The effects on the 2-substituted compound of alkyl, aryl and halogen substituents at the 4- and 5-positions were examined, but though the rates for the 5-substituents could be represented satisfactorily by cTp, substituted compounds. It is not surprising that the distorting effects of annular heteroatoms make it difficult to superimpose the substitution behavior of benzenoid compounds into this series. 

When polyalkyl- or polyhalobenzenes are treated with sulfuric acid, the ring is sulfonated, but rearrangement also takes place. The reaction, known as the Jacobsen reaction, is limited to benzene rings that have at least four substituents, which can be any combination of alkyl and halogen groups, where the alkyl groups can be... 

The effects on the 2-substituted compound of alkyl, aryl, and halogen substituents in the imidazole ring have also been examined, and although the rates for the 5-substituents were represented satisfactorily by quantum-mechanical calculations of 7c-electron densities for the imidazole neutral molecule predict the order of substitution as 5 > 4 > 2, but the tautomeric equivalence of the 4- and 5-positions is not taken into account. In addition, there are probably few occasions on which electrophilic substitution takes place with the neutral molecule the conjugate acid or conjugate base may be the reactive species. 

Analysis of NMR spectra of substituted aromatics by principal components analysis had shown that the substituents could be grouped into four stable classes Donors, acceptors, alkyls, and halogens. It was also shown that these groups were different to each other in their influence on the spectra. [10] As the NMR spectra reflect the electronic properties of the molecules, it was assumed that these groups would also represent different properties with regard to their chemical behaviour in chemical reactions. 

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