Chemistry
Nitration of Alkanes
Nitration of alkanes is a chemical reaction that involves the substitution of a hydrogen atom in an alkane with a nitro group. This reaction is typically carried out using a mixture of nitric acid and sulfuric acid as the nitrating agent. The resulting nitroalkane can be used as a precursor for the synthesis of various organic compounds.
Written by Perlego with AI-assistance
Related key terms
1 of 5
4 Key excerpts on "Nitration of Alkanes"
eBook - PDF- Walter Trahanovsky(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
B. Bachman, Η. B. Hass, and L. M. Addison, J. Org. Chem. 17, 906, 914, 928, 935, and 942 (1952). IV. Oxidations with Nitric Acid or Nitrogen Oxides 299 of oxygen enhances cleavage of C -C bonds which forms lower nitroalkanes. Addition of molecular bromine increases both the yield and conversion evidently by facilitating the formation of carbon radicals by hydrogen atom abstraction with atomic bromine. An increase in the surface-to-volume ratio results in an increase in selectivity of products. As shown in the nitration of butane [Eq. (1)], the reactivity of hydrogen atoms in alkanes increases only slightly in the order: primary < secondary < tertiary; the difference between the reactivities, however, is small. In another example, the nitration of pentane yields the following composition of products: 1-nitro, 18.9%; 2-nitro, 18.2%; and 3-nitro, 20.2%. These facts suggest a mechanism for the nitration involving alkyl radicals a n d -N 0 2 or OH. ΗΟΝ0 2 , ΗΟ· + · Ν 0 2 (2a) RH + -OH • R- + H 2 0 (2b) RH + · Ν 0 2 • R- + H N 0 2 (2c) R- + · Ν 0 2 > R -N 0 2 (2d) R'CH 2 - + · Ν 0 2 • RCH 2 0- + NO (2e) R'CH 2 0 • R - + CH 2 0 + etc. (2f) Thus, while nitration of arenes is a typical electrophilic substitution by N 0 2 + , the nitration of aliphatic compounds in the vapor phase involves hydrogen atom abstration followed either by coupling of the formed alkyl radicals with N 0 2 or further oxidation of the alkyl radicals. B. LIQUID PHASE OXIDATION Reaction of alkanes, cycloalkanes, and arylalkanes with nitric acid or nitrogen oxides in the liquid phase gives nitro compounds, nitrites, and carbonyl derivatives along with various oxidation and polynitration products. Alkyl and cycloalkylbenzenes are preferentially nitrated and oxidized at benzyl position. For example, ethylbenzene and cyclohexylbenzene give mainly α-nitroethylbenzene and α-nitrocyclohexylbenzene, respectively.
eBook - PDFAliphatic Compounds
A Modern Comprehensive Treatise
- S. Coffey(Author)
- 2016(Publication Date)
- Elsevier(Publisher)
In practice, the vapour phase process is run for the production of C lt C 2 , and C 3 nitroalkanes as the products of commercial interest. The addition of a small amount of air or oxygen to the reaction mixture is sometimes employed to increase the efficiency of the nitrating agent. Vapour phase nitration seems to involve a radical-chain reaction. Liquid phase Nitration of Alkanes was used long before the vapour phase process (F. Bcilstein and A. Kurbatov, Ber., 1880, 13, 1818). In this process tertiary hydrogen atoms are replaced more readily than secondary which, in turn, are more readily replaced than primary ones. Reaction is I NITRO- AND NITROSO-COMPOUNDS 95 slow and is accompanied by much oxidation and the production of large amounts of polynitroalkanes. (2) Replacement of halogen by a nitro group (Victor Meyer reaction) remains the best method for laboratory preparation of primary and secondary nitroalkanes. In its original form, reaction between alkyl hahdes and silver nitrite, fair yields of primary nitroalkanes could be obtained but the reaction was useless for the preparation of secondary (or tertiary) compounds and considerable amounts of by-products, mainly alkyl nitrites, were produced also. The mechanism of the reaction has been elucidated and a modified Victor Meyer synthesis evolved between alkyl hahdes and sodium nitrite in either dimethylformamide or dimethyl sulphoxide as solvent, by which means good yields of both primary and secondary nitroalkanes are obtained : w-C 6 H 13 -CHBr-CH 3 + NaN0 2 > NaBr + «-C 6 H l3 -CH(N0 2 )CH 3 (58%) (N. Kornblum et al., J. Amer. chem. Soc, 1955, 77, 5528, 6269; 1956, 78, 1497)· (3) Oxidation of aldoximes or ketoximes with peroxytrifluoroacetic acid gives good yields of primary and secondary nitroalkanes : (CH 3 -CH 2 -CH 2 ) 2 C:N-OH *-^^ ► (CH 3 -CH 2 -CH 2 ) 2 -CH-N0 2 (64%) (W. D. Emmons and A. S. Pagano, ibid., 1955, 77, 4557).
eBook - PDFMonohydric Alcohols Their Ethers and Esters Sulphur Analogues Nitrogen Derivatives Organometallic Compounds
A Modern Comprehensive Treatise
- S. Coffey(Author)
- 2016(Publication Date)
- Elsevier(Publisher)
In practice, the vapour phase process is run for the production of C lt C 2 , and C 3 nitroalkanes as the products of commercial interest. The addition of a small amount of air or oxygen to the reaction mixture is sometimes employed to increase the efficiency of the nitrating agent. Vapour phase nitration seems to involve a radical-chain reaction. Liquid phase Nitration of Alkanes was used long before the vapour phase process (F. Beilstein and A. Kurbatov, Ber., 1880, 13, 1818). In this process tertiary hydrogen atoms are replaced more readily than secondary which, in turn, are more readily replaced than primary ones. Reaction is I NITRO- AND NITROSO-COMPOUNDS 95 slow and is accompanied by much oxidation and the production of large amounts of polynitroalkanes. (2) Replacement of halogen by a nitro group (Victor Meyer reaction) remains the best method for laboratory preparation of primary and secondary nitroalkanes. In its original form, reaction between alkyl halides and silver nitrite, fair yields of primary nitroalkanes could be obtained but the reaction was useless for the preparation of secondary (or tertiary) compounds and considerable amounts of by-products, mainly alkyl nitrites, were produced also. The mechanism of the reaction has been elucidated and a modified Victor Meyer synthesis evolved between alkyl halides and sodium nitrite in either dimethylformamide or dimethyl sulphoxide as solvent, by which means good yields of both primary and secondary nitroalkanes are obtained: n-C e H 13 -CHBr-CH 3 + NaN0 2 > NaBr + w-C 6 H 13 -CH(N0 2 )CH 3 {58%) (N. Komblum et al., J. Amer. chem. Soc, 1955, 77, 5528, 6269; 1956, 78, 1497)· (3) Oxidation of aldoximes or ketoximes with peroxytrifluoroacetic acid gives good yields of primary and secondary nitroalkanes: CF CO H (CH 3 »CH 2 -CH 2 ) 2 C:N-OH ' 3 ► (CH 3 -CH 2 -CH 2 ) 2 -CH-N0 2 (64%) (W. D. Emmons and A. S. Pagano, ibid., 1955, 77, 4557).
eBook - PDF- Noboru Ono(Author)
- 2003(Publication Date)
- Wiley-Interscience(Publisher)
Alkyl anions are generally difficult to generate (pK a = ca. 50 for R-H) and hence unstable at room temperature, but the anions of nitroalkanes are generated readily (pK a = ca. 10 for RCH 2 NO 2 ), stable, and selective in the presence of other electron-withdrawing groups. The denitration reaction is now widely used for the synthesis of complex natural products with various functional groups. 7.2.1 Radical Denitration Denitrohydrogenation can be achieved either by radical or ionic processes. The first radical denitration was done with MeSNa in DMSO or HMPA (Eq. 7.45) 49 followed by heating with KOH in ethylene glycol (Eq. 7.46). 50 The reaction using MeSNa has played a pioneering role in this area. An electron-transfer chain mechanism has been proposed for these reactions, in which radical anions and free radicals are involved. The nitro groups, which are replaced by hydrogen using MeSNa, are limited to tertiary ones. Some of them are listed in Table 7.1. In 1981, Ono 51 and Tanner 52 reported independently that Bu 3 SnH is a more versatile reagent for denitrohydrogenation than MeSNa. A radical initiator, 2,2-azobisisobutyronitrile (AIBN) 51 or benzoylperoxide, 52 was used (see Table 7.1). α-Nitrocumene is converted into cumene in 92% yield on treatment with Bu 3 SnH (Eq. 7.47), whereas the yield is only 29% if the same conversion is carried out using MeSNa. Although several other radical denitration reagents such as 1,4-dihydronicotinamide (Eq. 7.48), 53 NaTeH (Eq. 7.49), 54 and Na 2 S 2 O 4 -Et 3 SiH (Eq. 7.50) 55 have been used, tin hydride is most widely employed for effecting this useful transformation. CN Me NO 2 Me HMPA CN Me H Me O O NO 2 Me Me Me HOCH 2 CH 2 OH O O H Me Me Me 25 ºC 50% 140 ºC 82% + KOH MeSNa + (7.45) (7.46) Me NO 2 Me AIBN Me H Me benzene 92% reflux Bu 3 SnH + (7.47) 7.2 R–H FROM R–NO 2 193 Table 7.1. Denitration of nitro compounds with MeSNa or Bu 3 SnH R-NO 2 Product Reagent Yield (%) Ref.
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
