Organic chemistry - Chapter 4: Alkanes - Nam Phan

Nội dung text: Organic chemistry - Chapter 4: Alkanes - Nam Phan

1. Chapter 4: ALKANES 2
2. ALKYL SUBSTITUENTS 4
3. • Substituents are listed in alphabetical order • Carbon chain is numbered with the lowest possible number in the compound Substituents are the same 6
4. PREPARATION OF ALKANES Catalytic hydrogenations of alkenes / alkynes 10
5. 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 12
6. 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
7. PRODUCT DISTRIBUTION It must be easier to abstract a hydrogen atom from a secondary carbon than from a primary carbon 18
8. Product distribution can be estimated: 20
9. Too violent Too slow 22
10. Already have 1 asymetric carbon 24