Isobutyl Groups H H H C-H C-H H H H H H-C-C-C-H H-C-C-C-H H H H HH isobutyl tert-butyl A primary carbon A tertiary carbon Chapter 3 11
Chapter 3 11 Isobutyl Groups H C H H C C H H C H H H H H C H H C C H H C H H H H H H A primary carbon A tertiary carbon => isobutyl tert-butyl
Alphabetize Alphabetize substituents by name. Ignore di-,tri-,etc.for alphabetizing. CH3 CH3 H3C-CH-CH-CH2-CH2-CH-CH3 CHCH: 3-ethyl-2,6-dimethylheptane => Chapter 3 12
Chapter 3 12 Alphabetize • Alphabetize substituents by name. • Ignore di-, tri-, etc. for alphabetizing. H3 C CH CH3 CH CH2 CH3 CH2 CH2 CH CH3 CH3 3-ethyl-2,6-dimethylheptane =>
Complex Substituents If the branch has a branch,number the carbons from the point of attachment. Name the branch off the branch using a locator number. Parentheses are used around the complex branch name. 1-methyl-3-(1,2-dimethylpropyl)cyclohexane => Chapter 3 13
Chapter 3 13 Complex Substituents • If the branch has a branch, number the carbons from the point of attachment. • Name the branch off the branch using a locator number. • Parentheses are used around the complex branch name. 1 2 3 1-methyl-3-(1,2-dimethylpropyl)cyclohexane =>
Physical Properties Solubility:hydrophobic Density:less than 1 g/mL Boiling points increase with increasing carbons(little less for branched chains). Melting points increase with increasing carbons(less for odd- number of carbons). Chapter 3
Chapter 3 14 Physical Properties • Solubility: hydrophobic • Density: less than 1 g/mL • Boiling points increase with increasing carbons (little less for branched chains). Melting points increase with increasing carbons (less for oddnumber of carbons). •
Boiling Points of Alkanes Branched alkanes have less surface area contact, so weaker intermolecular forces 400 300 CH3-(CH2)n-CH3 200 n-alkanes 100 CH3 0 CH-(CH2)CH3 -100 isoalkanes CH3 => -200 0 5 10 15 20 number of carbon atoms Chapter 3
Chapter 3 15 Boiling Points of Alkanes Branched alkanes have less surface area contact, so weaker intermolecular forces. =>