chapter 12 saturated hydrocarbons - alkanes
DESCRIPTION
Chapter 12 Saturated Hydrocarbons - Alkanes. Hydrocarbons. Compounds that contain only carbon and hydrogen Two classes: Aliphatic and aromatic. 2. The Petroleum Feedstock. Most alkanes come from petroleum Composed mostly of alkanes and aromatic hydrocarbons. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/1.jpg)
Chapter 12Saturated Hydrocarbons - Alkanes
![Page 2: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/2.jpg)
Hydrocarbons
• Compounds that contain only carbon and hydrogen• Two classes: Aliphatic and aromatic
2
![Page 3: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/3.jpg)
The Petroleum Feedstock• Most alkanes come from petroleum• Composed mostly of alkanes and aromatic
hydrocarbons
3
![Page 4: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/4.jpg)
4
![Page 5: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/5.jpg)
• Purification via fractional distillation
5
![Page 6: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/6.jpg)
![Page 7: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/7.jpg)
Physical Properties of Hydrocarbons
• Solubility: – Tend to be insoluble in water– Can be used for protective coatings– Good preservative for reactive metals
• Density:– Tend to have lower densities than water
• 0.6 g/mL – 0.8 g/mL
7
![Page 8: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/8.jpg)
![Page 9: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/9.jpg)
Boiling Points• Boiling point: Temperature at
which liquid turns to vapor– Temperature at which
vapor pressure of substance = atmospheric pressure
– B.P. of unbranched alkanes increases by approx. 20 – 30 °C per carbon
9
![Page 10: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/10.jpg)
Intermolecular Interactions for Alkanes
• Electron clouds can be temporarily distorted
10
![Page 11: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/11.jpg)
Intermolecular Interactions for Alkanes
• Induced dipole• van der Waals attraction (or a dispersion
interaction)• Greater intermolecular forces = higher b.p.
11
![Page 12: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/12.jpg)
Molecular Shape and Boiling Point
• Greater branching = lower b.p.• Molecules that are spherical have less surface area
12
![Page 13: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/13.jpg)
13
![Page 14: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/14.jpg)
Melting Points
• Melting point: Temperature at which a substance transforms from solid to liquid
• A narrow m.p. is an indicator of purity• Branching interferes with crystal packing
leading to lower m.p. values• Symmetric molecules tend to have unusually
high m.p’s
142.6 Physical Properties of Alkanes
![Page 15: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/15.jpg)
Melting Points
• M.P. increases with number of carbons
15
![Page 16: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/16.jpg)
Combustion
• Alkanes are the least reactive organic compounds
• Alkanes react rapidly with O2 in combustion
• A commercially important reaction with increasingly significant global impact
16
![Page 17: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/17.jpg)
Unbranched Alkanes
• Referred to as normal or n-alkanes• Possess a linear carbon chain
17
![Page 18: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/18.jpg)
![Page 19: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/19.jpg)
![Page 20: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/20.jpg)
20
![Page 21: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/21.jpg)
21
FormulasMolecular Formula
![Page 22: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/22.jpg)
Problems1) How many hydrogens does n-Octadecane,
an alkane containing 18 carbons, have?
2) Give the molecular, structural, condensed, and skeletal formulas for n-Octadecane
3) Estimate the boiling point and density of n-Octadecane
![Page 23: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/23.jpg)
Isomers• Compounds with the same molecular formula,
but different structural formula• Constitutional Isomers/Structural Isomers:
compounds with the same molecular formula but different atom connectivity
23C4H10
![Page 24: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/24.jpg)
Organic Nomenclature
• Standardized by International Union of Pure and Applied Chemistry (IUPAC)
• The current system is called substitutive nomenclature
• Rules for alkane nomenclature extend to most other compound classes
• Apply the following rules:
24
![Page 25: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/25.jpg)
Substitutive Nomenclature of Alkanes
1. Unbranched alkanes are named according to number of carbons
2. If branched, find the longest continuous carbon chain and identify this as the principle/parent chain
25
![Page 26: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/26.jpg)
Substitutive Nomenclature of Alkanes
3. If two chains are equal in length, select the one with the most substituents
4. Number the principle chain, giving the lower number to the first branching point
26
![Page 27: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/27.jpg)
Substitutive Nomenclature of Alkanes
5. Identify the name of each branch and to which carbon on the parent chain it is attached• Branching groups are called substituents• Those derived from alkanes are alkyl groups
27
![Page 28: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/28.jpg)
![Page 29: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/29.jpg)
• Methyl group
• Attached to C3 3-methyl
![Page 30: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/30.jpg)
30
6. Construct the namea. Location of branch (3)b. Name of branch (methyl)
• Note: a hyphen goes between the location and branch
c. Name of parent chain (hexane)
![Page 31: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/31.jpg)
Problems• Name the following molecules
![Page 32: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/32.jpg)
7. When more than one of the same substituent is present:– Indicate which carbon each substituent is on– Use Greek prefixes (di-, tri-, tetra-) to indicate how
many of each substituent you have
32
![Page 33: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/33.jpg)
Substitutive Nomenclature of Alkanes
8. For multiple substituents, select the numbering scheme that gives the smaller number at first point of difference
33
![Page 34: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/34.jpg)
9. Cite substituents in alphabetical order regardless of location
• Di-, tri-, tetra-, and hyphenated prefixes tert- and sec- are ignored
• Iso-, neo-, cyclo- are not ignored
34
![Page 35: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/35.jpg)
Problems• Name the following molecules:
![Page 36: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/36.jpg)
• Draw 2-bromo-3-chloro-4-fluoro-2,3,4-trimethylheptane
36
![Page 37: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/37.jpg)
10. If the numbering of different groups is not resolved, the first-cited group gets the lowest number
37
![Page 38: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/38.jpg)
Highly Condensed Structures
• Highly condensed structures are commonly used
38
![Page 39: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/39.jpg)
Classification of Carbon Substitution
• Primary (1°) carbon: A carbon bonded to 1 other carbon• Secondary (2°) carbon: A carbon bonded to 2 other
carbons• Tertiary (3°) carbon: A carbon bonded to 3 other
carbons• Quaternary (4°) carbon: A carbon bonded to 4 other
carbons
39
![Page 40: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/40.jpg)
Classification of Carbon Substitution
• Similarly, hydrogens may also be classified as primary, secondary, tertiary, or quaternary
40
![Page 41: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/41.jpg)
Problems
• Locate the primary, secondary, tertiary, and quaternary carbons in the following molecule
![Page 42: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/42.jpg)
Cycloalkanes
• Alkanes with closed loops or rings• Add the prefix cyclo
• Note that cyclohexane has 2 fewer hydrogens than hexane
42
![Page 43: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/43.jpg)
Nomenclature of Cyloalkanes
• The same nomenclature rules are followed• Do not forget the cyclo part of the name
• If the noncyclic carbon chain contains more carbons than the ring, it is named as the parent chain
43
![Page 44: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/44.jpg)
Problems• Name the following compounds
44
![Page 45: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/45.jpg)
45
![Page 46: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/46.jpg)
Problems• Draw the following compounds
1) 1-chloro-4-ethylcyclohexane
2) 2-bromo-1,1-dimethylcyclobutane
3) 1,1,2,2-tetramethylcyclopropane
![Page 47: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/47.jpg)
The “R” and “Ph” Notation
• A convenient way to represent a generic structure or portion of a molecule
• R Notation: R represents all alkyl groups
• A Benzene ring may be called a “phenyl group” and can be represented by Ph-
47
![Page 48: Chapter 12 Saturated Hydrocarbons - Alkanes](https://reader035.vdocument.in/reader035/viewer/2022062218/56816847550346895dde27ed/html5/thumbnails/48.jpg)
The “Ar” Notation
• Use Ar- for more highly substituted rings
48