TAILIEUCHUNG - Chapter 4: ALKANES

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 when the alkyl halides are bulky at the halogen-attached carbon. | 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@ Chapter 4: ALKANES NOMENCLATURE OF ALKANES ALKYL SUBSTITUENTS IUPAC NAMES OF BRANCHED ALKANES Determine the parent hydrocarbon – the longest continuous carbon chain Substituents are listed in alphabetical order Carbon chain is numbered with the lowest possible number in the compound Substituents are the same Di, tri, tetra, n, sec, and tert are ignored in alphabetizing substituents Iso, neo, and cyclo are not ignored NATURAL SOURCES OF ALKANES Natural gas & petroleum (fossil fuels) C1-4 C5-11 C9-16 C15-25 PREPARATION OF ALKANES Catalytic hydrogenations of alkenes / alkynes Reduction reactions 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 when the alkyl halides are bulky at the halogen-attached carbon Corey-House synthesis – the reaction of a lithium dialkyl cuprate with an alkyl halide to form a new alkane Corey-House synthesis overcomes some of the limitations of the Wurtz reaction REACTIVITY OF ALKANES Alkanes have only strong s 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 HALOGENATION OF ALKANES PRODUCT DISTRIBUTION It must be easier to abstract a hydrogen atom from a secondary carbon than from a primary carbon Reactivity - relative rate at which a particular hydrogen is abstracted in chlorination reactions: At room temperature Product distribution can be estimated: Br2 is less reactive towards alkane than Cl2, but Br2 is more selective Bromination at 125 oC Too violent Too slow STEREOCHEMISTRY OF RADICAL SUBSTITUTION REACTIONS Have no asymetric carbon Racemic mixture Already have 1 asymetric carbon COMBUSTION OF ALKANES

• Hoá học
• organic chemistry
• faculty of chemical engineering
• Isomerism
• Common reaction mechanisms
• alkanes
• In this workbook
• experiments are elaborated using small scale glassware and equipments from a Small Lab Kit
• developed at the Department of Chemistry
• Faculty of Science
• Chulalongkorn University in Thailand
• This Small Lab Kit was created as a result of the research project entitled “Chemistry Laboratory Based on Chemical Safety and Pollution Minimization” sponsored by Thai Research Fund (RDG 3 07 2543)
• One of the outcomes of this project is the organic laboratory book entitled “Organic Chemistry Laboratory Based on Chemical Safety and Pollution Minimization” written in Thai by professors from 7 universities in this project
• They compiled
• adjusted and tested the experiments taken from several traditional organic chemistry laboratory books using the prototype of Small Lab Kit
• Currently
• some selected experiments from this Thai organic chemistry laboratory text have further been modified
• rewritten and edited in English as appeared in this workbook
• Some experiments ar
• Ebook Organic chemistry
• Nucleophilic substitution
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