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Dr. Wolf's CHM 201 & 202 2- 1 2.11 IUPAC Nomenclature of Unbranched Alkanes.

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Presentation on theme: "Dr. Wolf's CHM 201 & 202 2- 1 2.11 IUPAC Nomenclature of Unbranched Alkanes."— Presentation transcript:

1 Dr. Wolf's CHM 201 & IUPAC Nomenclature of Unbranched Alkanes

2 Dr. Wolf's CHM 201 & Retained: methaneCH 4 ethaneCH 3 CH 3 propaneCH 3 CH 2 CH 3 butaneCH 3 CH 2 CH 2 CH 3 IUPAC Names of Unbranched Alkanes

3 Dr. Wolf's CHM 201 & Note: n-prefix is not part of IUPAC name of any alkane. For example: n-butane is "common name" for CH 3 CH 2 CH 2 CH 3 ; butane is "IUPAC name." Others: Latin or Greek prefix for number of carbons + ane suffix IUPAC Names of Unbranched Alkanes

4 Dr. Wolf's CHM 201 & Number of carbons NameStructure 5pentaneCH 3 (CH 2 ) 3 CH 3 6hexaneCH 3 (CH 2 ) 4 CH 3 7heptaneCH 3 (CH 2 ) 5 CH 3 8octaneCH 3 (CH 2 ) 6 CH 3 9nonaneCH 3 (CH 2 ) 7 CH 3 10decaneCH 3 (CH 2 ) 8 CH 3 IUPAC Names of Unbranched Alkanes

5 Dr. Wolf's CHM 201 & Number of carbons NameStructure 11undecaneCH 3 (CH 2 ) 9 CH 3 12dodecaneCH 3 (CH 2 ) 10 CH 3 13tridecaneCH 3 (CH 2 ) 11 CH 3 14tetradecaneCH 3 (CH 2 ) 12 CH 3 15pentadecaneCH 3 (CH 2 ) 7 CH 3 16hexadecaneCH 3 (CH 2 ) 8 CH 3 IUPAC Names of Unbranched Alkanes

6 Dr. Wolf's CHM 201 & Applying the IUPAC Rules: The Names of the C 6 H 14 Isomers

7 Dr. Wolf's CHM 201 & CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 (CH 3 ) 2 CHCH 2 CH 2 CH 3 (CH 3 CH 2 ) 2 CHCH 3 (CH 3 ) 2 CHCH(CH 3 ) 2 (CH 3 ) 3 CCH 2 CH 3 The C 6 H 14 Isomers

8 Dr. Wolf's CHM 201 & CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 The IUPAC name of the unbranched alkane with a chain of 6 carbons is hexane. Hexane The C 6 H 14 Isomers

9 Dr. Wolf's CHM 201 & Step 1) Find the longest continuous carbon chain and use the IUPAC name of the unbranched alkane as the basis. Step 2) Add name of substituent as a prefix. Step 3) Number the chain from the end nearest the substituent, and identify the carbon to which the substituent is attached by number. IUPAC Nomenclature of Branched Alkanes

10 Dr. Wolf's CHM 201 & (CH 3 ) 2 CHCH 2 CH 2 CH 3 (CH 3 CH 2 ) 2 CHCH 3 2-Methylpentane 3-Methylpentane The C 6 H 14 Isomers

11 Dr. Wolf's CHM 201 & (CH 3 ) 2 CHCH(CH 3 ) 2 (CH 3 ) 3 CCH 2 CH 3 2,3-Dimethylbutane 2,2-Dimethylbutane Use replicating prefixes (di-, tri-, tetra-, etc.) according to the number of identical substituents attached to the main chain. The C 6 H 14 Isomers

12 Dr. Wolf's CHM 201 & Alkyl Groups

13 Dr. Wolf's CHM 201 & Methyl and Ethyl Groups Methyl Ethyl C C HHHH H CH 3 CH 2 C HHH CH 3 or or

14 Dr. Wolf's CHM 201 & Unbranched Alkyl Groups If potential point of attachment is at the end of the chain, take the IUPAC name of the corresponding unbranched alkane and replace the -ane ending by -yl. R HR

15 Dr. Wolf's CHM 201 & Butyl If potential point of attachment is at the end of the chain, take the IUPAC name of the corresponding unbranched alkane and replace the -ane ending by -yl. R HR CH 3 CH 2 CH 2 CH 2 C C HHHH H C C HH H H or Unbranched Alkyl Groups

16 Dr. Wolf's CHM 201 & Hexyl CH 3 (CH 2 ) 4 CH 2 CH 3 (CH 2 ) 5 CH 2 CH 3 (CH 2 ) 16 CH 2 Heptyl Octadecyl Unbranched Alkyl Groups

17 Dr. Wolf's CHM 201 & The C 3 H 7 Alkyl Groups CH 3 CH 2 CH 2 C C H HH H H C H H or and CH 3 CHCH 3 C C H HH H H C H H or

18 Dr. Wolf's CHM 201 & CH 3 CH 2 CH 2 C C H HH H H C H H or IUPAC name: Propyl Common name: n-Propyl The C 3 H 7 Alkyl Groups

19 Dr. Wolf's CHM 201 & Naming Alkyl Groups (Table 2.7) Step 1:Identify longest continuous chain starting at point of attachment. Step 2: Drop -ane ending from name of unbranched alkane having same number of carbons as longest continuous chain and replace by -yl. Step 3:Identify substituents on longest continuous chain. Step 4:Chain is always numbered starting at point of attachment.

20 Dr. Wolf's CHM 201 & IUPAC name: 1-Methylethyl Common name: Isopropyl CH 3 CHCH 3 C C HHHH C H H or H The C 3 H 7 Alkyl Groups

21 Dr. Wolf's CHM 201 & CH 3 CH 2 CH 2 C C HHHH H C H H or Classification: Primary alkyl group Alkyl groups are classified according to the degree of substitution at the carbon that bears the point of attachment. A carbon that is directly attached to one other carbon is a primary carbon. The C 3 H 7 Alkyl Groups

22 Dr. Wolf's CHM 201 & Classification: Secondary alkyl group Alkyl groups are classified according to the degree of substitution at the carbon that bears the point of attachment. A carbon that is directly attached to two other carbons is a secondary carbon. CH 3 CHCH 3 C C HHHH C H H or H The C 3 H 7 Alkyl Groups

23 Dr. Wolf's CHM 201 & IUPAC name: Butyl Common name: n-Butyl Classification: Primary alkyl group CH 3 CH 2 CH 2 CH 2 C C HHHH H C C HH H H or The C 4 H 9 Alkyl Groups

24 Dr. Wolf's CHM 201 & IUPAC name: 1-Methylpropyl Common name: sec-Butyl Classification: Secondary alkyl group CH 3 CHCH 2 CH 3 C C H HH H H C C HH H H or12 3 The C 4 H 9 Alkyl Groups

25 Dr. Wolf's CHM 201 & IUPAC name: 2-Methylpropyl Common name: Isobutyl Classification: Primary alkyl group C H CH 2 CH 3 The C 4 H 9 Alkyl Groups

26 Dr. Wolf's CHM 201 & IUPAC name: 1,1-Dimethylethyl Common name: tert-Butyl Classification: Tertiary alkyl group 1 2 C CH 3 The C 4 H 9 Alkyl Groups

27 Dr. Wolf's CHM 201 & IUPAC Names of Highly Branched Alkanes

28 Dr. Wolf's CHM 201 & Branched alkanes Octane

29 Dr. Wolf's CHM 201 & Ethyloctane Branched alkanes

30 Dr. Wolf's CHM 201 & Ethyl-3-methyloctane List substituents in alphabetical order. Branched alkanes

31 Dr. Wolf's CHM 201 & Ethyl-3,5-dimethyloctane List substituents in alphabetical order. But don't alphabetize di-, tri-, tetra-, etc. Branched alkanes

32 Dr. Wolf's CHM 201 & First Point of Difference Rule The chain is numbered in the direction that gives the lower locant to the substituent at the first point of difference in the names. Don't add locants! 2,2,6,6,7-Pentamethyloctane? 2,3,3,7,7-Pentamethyloctane? What is correct name?

33 Dr. Wolf's CHM 201 & First Point of Difference Rule The chain is numbered in the direction that gives the lower locant to the substituent at the first point of difference in the names. Don't add locants! 2,2,6,6,7-Pentamethyloctane? What is correct name?

34 Dr. Wolf's CHM 201 & CnH2nCnH2nCnH2nCnH2n 2.15 Cycloalkane Nomenclature

35 Dr. Wolf's CHM 201 & CycloalkanesCycloalkanes Cycloalkanes are alkanes that contain a ring of three or more carbons. Count the number of carbons in the ring, and add the prefix cyclo to the IUPAC name of the unbranched alkane that has that number of carbons. CyclopentaneCyclohexane

36 Dr. Wolf's CHM 201 & Ethylcyclopentane CycloalkanesCycloalkanes CH 2 CH 3 Name any alkyl groups on the ring in the usual way.

37 Dr. Wolf's CHM 201 & Name any alkyl groups on the ring in the usual way. List substituents in alphabetical order and count in the direction that gives the lowest numerical locant at the first point of difference. 3-Ethyl-1,1-dimethylcyclohexane CH 2 CH 3 H3CH3CH3CH3C CH 3 CycloalkanesCycloalkanes

38 Dr. Wolf's CHM 201 & Sources of Alkanes and Cycloalkanes

39 Dr. Wolf's CHM 201 & Crude oil

40 Dr. Wolf's CHM 201 & Crude oil Refinery gas C 1 -C 4 Light gasoline (bp: °C) Light gasoline (bp: °C) C 5 -C 12 Naphtha (bp °C) Naphtha Kerosene (bp: °C) Kerosene C 12 -C 15 Gas oil (bp: °C) Gas oil (bp: °C) C 15 -C 25 ResidueResidue

41 Dr. Wolf's CHM 201 & Cracking converts high molecular weight hydrocarbons to more useful, low molecular weight ones Reforming increases branching of hydrocarbon chains branched hydrocarbons have better burning characteristics for automobile engines Petroleum Refining

42 Dr. Wolf's CHM 201 & Physical Properties of Alkanes and Cycloalkanes

43 Dr. Wolf's CHM 201 & Boiling Points of Alkanes governed by strength of intermolecular attractive forces alkanes are nonpolar, so dipole-dipole and dipole-induced dipole forces are absent only forces of intermolecular attraction are induced dipole-induced dipole forces

44 Dr. Wolf's CHM 201 & Induced dipole-Induced dipole attractive forces + – + – two nonpolar molecules center of positive charge and center of negative charge coincide in each

45 Dr. Wolf's CHM 201 & – + – movement of electrons creates an instantaneous dipole in one molecule (left) Induced dipole-Induced dipole attractive forces

46 Dr. Wolf's CHM 201 & – + – temporary dipole in one molecule (left) induces a complementary dipole in other molecule (right) Induced dipole-Induced dipole attractive forces

47 Dr. Wolf's CHM 201 & – + – temporary dipole in one molecule (left) induces a complementary dipole in other molecule (right) Induced dipole-Induced dipole attractive forces

48 Dr. Wolf's CHM 201 & – + – the result is a small attractive force between the two molecules Induced dipole-Induced dipole attractive forces

49 Dr. Wolf's CHM 201 & – + – the result is a small attractive force between the two molecules Induced dipole-Induced dipole attractive forces

50 Dr. Wolf's CHM 201 & increase with increasing number of carbons more atoms, more electrons, more opportunities for induced dipole-induced dipole forces decrease with chain branching branched molecules are more compact with smaller surface area—fewer points of contact with other molecules Boiling Points

51 Dr. Wolf's CHM 201 & increase with increasing number of carbons more atoms, more electrons, more opportunities for induced dipole-induced dipole forces Heptane bp 98°C Octane bp 125°C Nonane bp 150°C Boiling Points

52 Dr. Wolf's CHM 201 & decrease with chain branching branched molecules are more compact with smaller surface area—fewer points of contact with other molecules Octane: bp 125°C 2-Methylheptane: bp 118°C 2,2,3,3-Tetramethylbutane: bp 107°C Boiling Points

53 Dr. Wolf's CHM 201 & All alkanes burn in air to give carbon dioxide and water Chemical Properties: Combustion of Alkanes

54 Dr. Wolf's CHM 201 & increase with increasing number of carbons more moles of O 2 consumed, more moles of CO 2 and H 2 O formed Heats of Combustion

55 Dr. Wolf's CHM 201 & kJ/mol 5471 kJ/mol 6125 kJ/mol 654 kJ/mol Heptane Octane Nonane Heats of Combustion

56 Dr. Wolf's CHM 201 & increase with increasing number of carbons more moles of O 2 consumed, more moles of CO 2 and H 2 O formed decrease with chain branching branched molecules are more stable (have less potential energy) than their unbranched isomers Heats of Combustion

57 Dr. Wolf's CHM 201 & kJ/mol 5466 kJ/mol 5458 kJ/mol 5452 kJ/mol 5 kJ/mol 8 kJ/mol 6 kJ/mol Heats of Combustion

58 Dr. Wolf's CHM 201 & Isomers can differ in respect to their stability. Equivalent statement: Isomers differ in respect to their potential energy. Differences in potential energy can be measured by comparing heats of combustion. Important Point

59 Dr. Wolf's CHM 201 & CO 2 + 9H 2 O 5452 kJ/mol 5458 kJ/mol 5471 kJ/mol 5466 kJ/mol O2O2O2O O2O2O2O O2O2O2O O2O2O2O Figure 2.14


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