Download presentation
Presentation is loading. Please wait.
1
Alkanes C H n 2n+2 all C are sp3 hybridized 4 bonds 109.5o n root
suffix formula 3 prop ane C3H8 4 but ane C4H10 5 pent ane C5H12 6 hex ane C6H14 7 hept ane C7H16 8 oct ane C8H18 9 non ane C9H20 10 dec ane C10H22 1 meth ane C H 4 2 eth ane C2H6 s p sp3 atomic orbitals
2
Alkanes London Dispersion Forces n = 1-4 gases n = 5-15 liquids
compound m.w. b.p.(Co) CH C2H C3H C4H C5H n = gases n = liquids n > solids
3
Alkanes IMF = q1q2 r 72 36.1 72 27.9 72 9.5 structural isomers
____ compound m.w. b.p. 72 36.1 72 27.9 72 9.5 structural isomers same formula different shape r branching
5
Reactions of Alkanes Substitution of halogens
Cl2 2Cl. step 1 initiation step 2 Cl.+ CH4 CH3. + HCl propagation step 3 CH3.+ Cl2 CH3Cl + Cl. propagation step 4 Cl.+ Cl. Cl2 termination get a mixture of chlorinated methanes
6
Halogenation of Alkanes
CH3Cl chloro methane methyl chloride CH2Cl2 di chloromethane methylene chloride CHCl3 tri chloromethane chloroform CCl4 tetra chloromethane carbon tetrachloride all liquids at room temperature methane is gas e- rich Cl increases LDF dipole moments Which are soluble in H2O? polar solvent
7
Nomenclature 1. Pick longest C chain as parent
2. Number C beginning at end with first branch 3. Identify branching substituents Assign each a number 4. Use commas to separate numbers hyphens to separate numbers from names 5. Alphabetize substituents
8
Nomenclature Structural isomers of C5H12 I. III. II. I. pentane II. 2-
4 1 3 2 1 2 2 3 3 4 4 II. 1 1 2 3 I. pentane II. 2- methyl butane III. 2,2- di methyl propane
9
Nomenclature R = “alkyl” group 1o 3o primary carbon tertiary carbon 4o
secondary carbon quaternary carbon
10
Nomenclature “common” names to learn: iso propyl alphabetized as i
sec- butyl alphabetized as b iso butyl alphabetized as i tert- butyl alphabetized as b
11
Nomenclature heptane heptane heptane 3 branches 2 branches 4 branches
1 2 1 3 7 3 1 3 5 7 4 6 4 2 4 6 5 2 5 6 7 heptane heptane heptane 3 branches 2 branches 4 branches
12
Nomenclature 3,5-diethyl -2-methyl -4-propyl heptane 2- methyl methyl
1 2 2- methyl methyl 3- ethyl 3 5 7 4 6 4- ethyl propyl propyl 5- ethyl 3,5-diethyl 3,5-diethyl -2-methyl -4-propyl heptane
13
Cycloalkanes linear alkanes CnH2n+2 branched alkanes cycloalkanes
closed rings CnH2n 2 cyclo propane 3 1 bond angle = 60o tetrahedral angle = 109o very unstable
14
Cycloalkanes cyclobutane bond angle = 88o tetrahedral angle = 109o
unstable
15
Cycloalkanes cyclopentane bond angle = 108o tetrahedral angle = 109o
stable
16
Cycloalkanes cyclohexane predicted bond angle = 120o
tetrahedral angle = 109o stable
17
Cycloalkanes geometric isomers cis- 1,3- dichloro cyclo butane trans-
- - cis- 1,3- dichloro cyclo butane trans- 1,3- dichloro cyclo butane
18
Optical isomerism 3-methyl hexane bromo chloro iodo methane bromo
Stereocenter 4 different substituents * * 3-methyl hexane bromo chloro iodo methane * * bromo cyclo pentane trans- 1,3-dibromo cyclopentane no C*
19
Alkane Summary 1. Alkanes - sp3 hybridized 2. Relatively unreactive
Substitution with halogens Combustion 3. Non-polar IMF = London Dispersion Forces size structure
20
4. Free rotation around C-C bonds
conformations 5. Non-cyclic alkanes - structural isomers 6. Cyclic alkanes - geometric isomers cis-, trans- 7. Alkanes - optical isomers stereocenters C*
Similar presentations
