1 ORGANIC CHEMISTRY Dr Nam T. S. Phan Faculty of Chemical Engineering HCMC University of Technology Office: room 211, B2 Building Phone: 8647256 ext. 5681 Email: ptsnam@hcmut.edu.vn 2 Chapter 4: ALKANES 3 NOMENCLATURE OF ALKANES 4 ALKYL SUBSTITUENTS 5 IUPAC NAMES OF BRANCHED ALKANES Determine the parent hydrocarbon – the longest continuous carbon chain 6 • Substituents are listed in alphabetical order • Carbon chain is numbered with the lowest possible number in the compound Substituents are the same 7 • Di, tri, tetra, n, sec, and tert are ignored in alphabetizing substituents • Iso, neo, and cyclo are not ignored 8 9 NATURAL SOURCES OF ALKANES Natural gas & petroleum (fossil fuels) C1-4 C5-11 C9-16 C15-25 10 PREPARATION OF ALKANES Catalytic hydrogenations of alkenes / alkynes [...]... overcomes some of 13 the limitations of the Wurtz reaction REACTIVITY OF ALKANES • Alkanes have only strong σ bonds • Electronegativity of C & H are approximately the same • None of the atoms in alkanes have any significant charge • Neither nucleophiles nor electrophiles are attracted Alkanes are very unreactive 14 HALOGENATION OF ALKANES 15 16 17 PRODUCT DISTRIBUTION It must be easier to abstract a hydrogen...Reduction reactions 11 Wurtz reactions symmetric alkane Limitations: + The Wurtz reaction is limited to the synthesis of symmetric alkanes from alkyl iodides & bromides + If two dissimilar alkyl halides are taken as reactants, then the product is a mixture of alkanes that is, often, difficult to separate + A side reaction also occurs to produce an alkene + The side reaction becomes more significant... selective Bromination at 125 oC 21 Too violent Too slow 22 STEREOCHEMISTRY OF RADICAL SUBSTITUTION REACTIONS Have no asymetric carbon Racemic mixture 23 Already have 1 asymetric carbon 24 COMBUSTION OF ALKANES 25 . 8647256 ext. 5681 Email: ptsnam@hcmut.edu.vn 2 Chapter 4: ALKANES 3 NOMENCLATURE OF ALKANES 4 ALKYL SUBSTITUENTS 5 IUPAC NAMES OF BRANCHED ALKANES Determine the parent hydrocarbon – the longest. Wurtz reaction 14 REACTIVITY OF ALKANES • Alkanes have only strong σ bonds • Electronegativity of C & H are approximately the same • None of the atoms in alkanes have any significant charge • . the synthesis of symmetric alkanes from alkyl iodides & bromides + If two dissimilar alkyl halides are taken as reactants, then the product is a mixture of alkanes that is, often, difficult