Chapter 3. An Introduction to Organic Compounds. Spring Alkanes are hydrocarbons containing only single bonds General formula: C n H 2n+2

Transcription

1 Chapter 3 An Introduction to Organic Compounds Nomenclature, Physical Properties, and Representation of structure Alkanes are hydrocarbons containing only single bonds General fmula: C n H 2n+2 1

2 Constitutional isomers have the same molecular fmula, but their atoms are linked differently Nomenclature of Alkyl Substituents 2

3 A compound can have me than one name, but a name must specify only one compound A C 7 H 16 compound can be any one of the following: 3

4 Different Kinds of Carbons and Hydrogens Nomenclature of Alkanes 1. Determine the number of carbons in the parent hydrocarbon CH 2 CH 2 CH 2 CHCH 2 CH CH 2 CH 2 CH 2 CHCH 2 CH 2 CH CH 2 CH 2 CHCH 2 CH 2 CH 2 CH 2 CH Number the chain so that the substituent gets the lowest possible number CHCH 2 CH 2 2-methylpentane CH 2 CH 2 CHCH 2 CH 2 CH 2 CH 4-isopropyloctane CHCH 2 CH 2 common name: isohexane systematic name: 2-methylpentane 4

5 3. Number the substituents to yield the lowest possible number in the number of the compound CH 2 CHCH 2 CHCH 2 CH 2 CH 2 5-ehtyl-3-methyloctane 4-ethyl-6-methyloctane because 3<4 (substituents are listed in alphabetical der) 4. Assign the lowest possible numbers to all of the substituents CH 2 CH 2 CHCH 2 CH CH 2 CH 2 C CCH 2 CH 2 CCH 2 CH 2 CHCH 2,4-dimethylhexane 3,3,4,4-tetramethylheptane CH 2 CH 2 3,3,6-triethyl-7-methyldecane 5. When both directions lead to the same lowest number f one of the substituents, the direction is chosen that gives the lowest possible number to one of the remaining substituents CHCH 2 CH 2,2,4-trimethylpentane 2,4,4-trimethylpentane because 2<4 CH 2 CHCHCH 2 CHCH 2 CH 2 6-ethyl-3,4-dimethyloctane 3-ethyl-5,6-dimethyloctane because 4<5 6. If the same number is obtained in both directions, the first group receives the lowest number Cl CHCH Br 2-bromo-3-chlobutane 3-bromo-2-chlobutane CH 2 CH 2 CHCH 2 CHCH 2 3-ethyl-5-methylheptane 5-ethyl-3-methylheptane 5

6 7. In the case of two hydrocarbon chains with the same number of carbons, choose the one with the most substituents CH 2 CHCH 2 CH 2 2 CH 1 3-ethyl-2-methylhexane (two substituents) CH 2 CHCH 2 CH 2 CH 3-isopropylhexane (one substituent) 8. Certain common nomenclatures are used in the IUPAC system CH 2 CH 2 CH 2 CHCH 2 CH 2 CH 4-isopropyloctane 4-(1-methylethyl)octane CH 2 CH 2 CH 2 CHCH 2 CH 2 CH 2 CH 2 CH 2 CH 5-isobutyldecane 5-(2-methylpropyl)decane Nomenclature of Cycloalkanes 1. No number is needed f a single substituent on a ring CH 2 CH 2 CH 2 CH 2 CH 2 methylcyclopentane ethylcyclohexane 1-cyclobutylpentane 2. Name the two substituents in alphabetical der H 3 C CH 2 CH 2 1-methyl-2-propylcyclopentane H 3 CH 2 C 1-ethyl-3-methylcyclopentane 1,3-dimethylcyclohexane 6

7 3. If there are me than two substituents, CH 2 CH 2 H 3 C CH 2 4-ethyl-2-methyl-1-propylcyclohexane 1-ethyl-3-methyl-4-propylcyclohexane because2<3 5-ethyl-1-methyl-2-propylcyclohexane 1,1,2-trimethylcyclopentane 1,2,2-trimethylcyclopentane because1<2 1,1,5-trimethylcyclopentane because 2<5 Nomenclature of Alkyl Halides Cl CH 2 F CHI CH 2 CHBr chlomethane fluoethane 2-iodopropane 2-bromobutane In the IUPAC system, alkyl halides are named as substituted alkanes CH 2 CHCH 2 CH 2 CH Br 2-bromo-5-methylheptane Br CCHCH 2 CH 2 CH 2 Cl 1-chlo-5,5-dimethylhexane I CH 2 Cl 1-ethyl-2-iodocyclopentane 4-bromo-2-chlo-1-methylcyclohexane 7

8 Different Kinds of Alkyl Halides Nomenclature of Ethers OCH 2 CH 2 OCH 2 CHCH 2 OC ethyl methyl ether diethyl ether tert-butyl isobutyl ether CHOCHCH 2 sec-butyl isopropyl ether CHCH 2 CH 2 O cyclohexyl isopentyl ether As substituents: O methoxy CH 2 O ethoxy CHO isopropoxy CH 2 CHO sec-butoxy C O tert-butoxy 8

9 Nomenclature of Alcohols In an alcohol, the OH is a functional group A functional group is the center of reactivity in a molecule 1. Determine the parent hydrocarbon containing the functional group CHCH 2 OH 2-butanol butan-2-ol CH 2 CH 2 CHCH 2 OH CH 2 2-ethyl-1-pentanol 2-ethylpentan-1-ol CH 2 CH 2 CH 2 OCH 2 CH 2 CH 2 OH 3-butoxy-1-propanol 3-butoxypropan-1-ol The functional group suffix should get the lowest number HOCH 2 CH 2 CH 2 Br 3-bromo-1-propanol ClCH 2 CH 2 CH OH 4-chlo-2-butanol CCH 2 CH OH 4,4-dimethyl-2-pentanol 3. When there is both a functional group suffix and a substituent, the functional group suffix gets the lowest number. And the substituent gets the second lowest number possible. CHCHCH 2 Cl OH 2-chlo-3-pentanol 4-chlo-3-pentanol CH 2 CH 2 CHCH 2 CH OH 2-methyl-4-heptanol 6-methyl-4-heptanol OH 3-methylcyclohexanol 5-methylcyclohexanol 9

10 4. If there is me than one substituent, the substituents are cited in alphabetical der CH 2 CH 2 CHCH 2 CHCH 2 CH Br OH H 3 C OH 6-bromo-4-ethyl-2-heptanol 2-ethyl-5-methylcyclohexanol HO 3,4-dimethylcyclopentanol CH 2 CH 2 CH 2 NH 2 1-butanamine butan-1-amine Nomenclature of Amines CH 2 CHCHCH 2 NHCH 2 N-ethyl-3-hexanamine N-ethylhexan-3-amine CH 2 CH 2 NCH 2 N-ethyl-N-methyl-1-propanamine N-ethyl-N-methylpropan-1-amine The substituents are listed in alphabetical der and a number an N is assigned to each one 4 3 CHCH 2 CH 2 N Cl 2 3-chlo-N-methyl-1-butanamine 1 CH 2 NHCH 2 CH CH 2 CHCHCH NHCH 2 N-ethyl-5-methyl-3-hexanamine Br CHCHCH H 3 C N 4-bromo-N,N-dimethyl-2-pentanamine 2-ethyl-N-propylcyclohexanamine 10

11 Naming Quaternary Ammonium Salts Spring 2017 H 3 C N + - HO CH 2 CH N + 3 CH 2 CH 2 Cl - tetramethylammonium hydroxide ethyldimethylpropylammonium chlide Structures of Alkyl Halides 11

12 Structures of Alcohol and Ether Structures of Amines 12

13 Attractive Fces van der Waals fce Dipole dipole interaction Hydrogen bonds The greater the attractive fces between molecules, the higher is the boiling point of the compound van der Waals Fces The boiling point of a compound increases with the increase in van der Waals fces 13

14 Dipole Dipole Interaction Dipole dipole interactions are stronger than van der Waals fces but weaker than ionic covalent bonds A hydrogen bond is a special kind of dipole dipole interaction 14

15 Like Dissolves Like Polar compound dissolves in polar solvent Nonpolar compound dissolves in nonpolar solvent 15