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Chapter 22 “Hydrocarbon Compounds”. Pre-AP Chemistry Charles Page High School Stephen L. Cotton. (C 4 H 10 ). Section 22.1 Hydrocarbons. OBJECTIVES: Describe the relationship between number of valence electrons and bonding in carbon . Section 22.1 Hydrocarbons. OBJECTIVES:

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chapter 22 hydrocarbon compounds

Chapter 22“Hydrocarbon Compounds”

Pre-AP Chemistry

Charles Page High School

Stephen L. Cotton

(C4H10)

section 22 1 hydrocarbons
Section 22.1Hydrocarbons
  • OBJECTIVES:
    • Describe the relationship between number of valence electrons and bonding in carbon.
section 22 1 hydrocarbons3
Section 22.1Hydrocarbons
  • OBJECTIVES:
    • Define and describe alkanes.
section 22 1 hydrocarbons4
Section 22.1Hydrocarbons
  • OBJECTIVES:
    • Relate the polarity of hydrocarbons to their solubility.
organic chemistry and hydrocarbons
Organic Chemistry and Hydrocarbons
  • “Organic” originally referred to any chemicals that came from organisms
  • 1828 - German chemist Friedrich Wohler synthesized urea in a lab
  • Today, organic chemistry is the chemistry of virtually all compounds containing the element carbon
slide6

Friedrich Wohler

  • 1800 – 1882
  • Used inorganic substances to synthesize urea, a carbon compound found in urine.
  • This re-defined organic chemistry.
organic chemistry and hydrocarbons7
Organic Chemistry and Hydrocarbons
  • Over a million organic compounds, with a dazzling array of properties
  • Why so many? Carbon’s unique bonding ability!
  • Let’s start with the simplest of the organic compounds. These are the Hydrocarbons
organic chemistry and hydrocarbons8
Organic Chemistry and Hydrocarbons
  • Hydrocarbons contain only two elements: 1) hydrogen, and 2) carbon
    • simplest hydrocarbons called “alkanes”, which contain only carbon to carbon singlecovalent bonds (CnH2n+2)
    • methane (CH4) with one carbon is the simplest alkane. It is the major component of natural gas
organic chemistry and hydrocarbons9
Organic Chemistry and Hydrocarbons
  • Review structural formulas - p.694
  • Carbon has 4 valence electrons, thus forms 4 covalent bonds
    • not only with other elements, but also forms bonds WITH ITSELF (nonpolar)
  • Ethane (C2H6) is the simplest alkane with a carbon to carbon bond
straight chain alkanes
Straight-Chain Alkanes
  • Straight-chain alkanes contain any number of carbon atoms, one after the other, in a chain pattern - meaning one linked to the next (not always straight)

C-C-C C-C-C-C etc.

  • Names of alkanes always will always end with -ane
straight chain alkanes11
Straight-Chain Alkanes
  • Combined with the -ane ending is a prefix for the number of carbons
    • Table 22.1, page 695
  • Homologous series- a group of compounds that have a constant increment of change
  • In alkanes, it is: -CH2- (methylene)
straight chain alkanes12
Straight-Chain Alkanes
  • Many alkanes used for fuels: methane, propane, butane, octane
  • As the number of carbons increases, so does the boiling and melting pt.
    • The first 4 are gases; #5-15 are liquids; higher alkanes are solids
  • Condensed structural formulas? Note examples on page 696
naming straight chain alkanes
Naming Straight-Chain Alkanes
  • Names recommended by IUPAC - the International Union of Pure and Applied Chemistry
    • end with –ane; the root part of the name indicates the # of carbons
  • We sometimes still rely on common names, some of which are well-known
naming straight chain alkanes14
Naming Straight-Chain Alkanes
  • IUPAC names may be long and cumbersome
  • Common names may be easier or more familiar, but usually do not describe the chemical structure!
    • Methane is natural gas or swamp gas
branched chain alkanes
Branched-Chain Alkanes
  • Branched-chain means that other elements besides hydrogen may be attached to the carbon
    • halogens, oxygen, nitrogen, sulfur, and even other carbons
    • any atom that takes the place of a hydrogen on a parent hydrocarbon is called a substituent, or the branchedpart
branched chain alkanes16
Branched-Chain Alkanes
  • A hydrocarbon substituent is called an alkyl group or sometimes radicals
    • use the same prefixes to indicate the number of carbons, but -ane ending is now -yl such as: methyl, ethyl, propyl, etc.
  • Gives much more variety to the organic compounds
branched chain alkanes17
Branched-Chain Alkanes
  • Rules for naming – go from right to left - page 698

1. Longest C-C chain is parent

2. Number so branches have lowest #

3. Give position number to branch

4. Prefix (di, tri) more than one branch

5. Alphabetize branches (not prefix)

6. Use proper punctuation ( - and , )

branched chain alkanes19
Branched-Chain Alkanes
  • From the name, draw the structure, in a right-to-left manner:

1. Find the parent, with the -ane

2. Number carbons on parent

3. Identify substituent groups (give lowest number); attach

4. Add remaining hydrogens

alkanes
Alkanes
  • Draw 3-ethylpentane
  • Draw 2,3,4-trimethylhexane
  • Since the electrons are shared equally, the molecule is nonpolar
    • thus, not attracted to water
    • oil (a hydrocarbon) not soluble in H2O
    • “like dissolves like”
section 22 2 unsaturated hydrocarbons
Section 22.2Unsaturated Hydrocarbons
  • OBJECTIVES:
    • Describe the difference between unsaturated and saturated hydrocarbons.
section 22 2 unsaturated hydrocarbons23
Section 22.2Unsaturated Hydrocarbons
  • OBJECTIVES:
    • Distinguish the structures of alkenes and alkynes.
alkenes
Alkenes
  • Multiple bonds can also exist between the carbon atoms
  • Hydrocarbons containing carbon to carbon double bonds are called alkenes(CnH2n) C=C C-C=C
  • Called “unsaturated” if they contain double or triple bonds
naming alkenes
Naming Alkenes
  • Find longest parent that has the double bond in it
  • New ending: -ene
  • Number the chain, so that the double bond gets the lower number
  • Name and number the substituents
  • Samples on page 702
alkynes
Alkynes
  • Hydrocarbons containing carbon to carbon triple bonds are called alkynes

(CnH2n-2) -C C-

  • Alkynes are not plentiful in nature
  • Simplest is ethyne- common name acetylene (fuel for torches)
  • Table 22.3, p. 703 for boiling pt.

ethyne

section 22 3 isomers
Section 22.3Isomers
  • OBJECTIVES:
    • Explain why structural isomers have different properties.
section 22 3 isomers28
Section 22.3Isomers
  • OBJECTIVES:
    • Describe the conditions under which geometric isomers are possible.
section 22 3 isomers29
Section 22.3Isomers
  • OBJECTIVES:
    • Identify optical isomers.
structural isomers
Structural Isomers
  • Compounds that have the same molecular formula, but different molecular structures, are called structural isomers
  • Butane and 2-methylpropane (made by breaking carbon off the end, and making it a branch in the middle)
  • Also have different properties, such as b.p., m.p., and reactivity
stereoisomers
Stereoisomers
  • Don’t forget that these structures are really 3-dimensional
  • stereoisomers- molecules of the same molecular structure that differ only in the arrangement of the atoms in space. Two types are a) geometric and b) optical
geometric isomers
Geometric Isomers
  • There is a lack of rotation around a carbon to carbon multiple bond
    • has an important structural implication
    • Two possible arrangements:

1.trans configuration - substituted groups on opposite sides of double bond

2. cisconfiguration - same side

slide34

Geometric Isomers

Substituted groups are on opposite sides of the double bond (in this case, one is above, the other is below)

Trans-2-butene

Substituted groups are on the same side of the double bond (in this case, both are above)

Cis-2-butene

geometric isomers35
Geometric Isomers
  • Trans-2-butene and Cis-2-butene shown on page 705
  • differ in the geometry of the substituted groups (to double bond)
  • like other structural isomers, have different physical and chemical properties ( note page 705-middle)
optical isomers
Optical Isomers
  • Asymmetric carbon? C with 4 different groups attached. Conceptual Problem 22.4, p.706
  • Molecules containing asymmetric carbons have “handedness”, and exist as stereoisomers.
    • Figure 22.9, page 705
slide37

Optical Isomers, and these will each show an asymetric carbon (4 different branches attached)

The asymetric carbon

section 22 4 hydrocarbon rings
Section 22.4Hydrocarbon Rings
  • OBJECTIVES:
    • Identify cyclic ring structures.
section 22 4 hydrocarbon rings39
Section 22.4Hydrocarbon Rings
  • OBJECTIVES:
    • Describe bonding in benzene.
cyclic hydrocarbons
Cyclic Hydrocarbons
  • The two ends of the carbon chain are attached in a ring in a cyclic hydrocarbon
    • sample drawings on page 709
    • named as “cyclo- ____”
  • hydrocarbon compounds that do NOT contain rings are known as aliphatic compounds
aromatic hydrocarbons
Aromatic Hydrocarbons
  • A special group of unsaturated cyclic hydrocarbons is known as arenes
    • contain single rings, or groups of rings
    • also called “aromatic hydrocarbons”, because of pleasant odor
    • simplest aromatic is benzene (C6H6)
    • Term “aromatic” applies to materials with bonding like that of benzene
aromatic hydrocarbons42
Aromatic Hydrocarbons
  • Benzene is a six-carbon ring, with alternating double and single bonds
    • exhibits resonance, due to location of the double and single bonds-p.710
  • Benzene derivatives possible:
    • methylbenzene, 3-phenylhexane, ethylbenzene (top page 711)
aromatic hydrocarbons43
Aromatic Hydrocarbons
  • One derivative of Benzene is called phenylethene, or commonly named STYRENE.
  • Foamed styrene is trademarked by Dow Chemical as “styrofoam”
  • Other manufacturers items usually just called “foam cups”

CH2

CH

aromatic hydrocarbons44
Aromatic Hydrocarbons
  • Benzene derivatives can have two or more substitutents:
    • 1,2-dimethylbenzene
    • 1,3-dimethylbenzene
    • 1,4-dimethylbenzene
  • Can use ortho for 1,2; meta for 1,3; and para for 1,4 (page 711)

C

C

C

C

section 22 5 hydrocarbons from earth s crust
Section 22.5Hydrocarbons From Earth’s Crust
  • OBJECTIVES:
    • Identify three important fossil fuels and describe their origins.
section 22 5 hydrocarbons from earth s crust46
Section 22.5Hydrocarbons From Earth’s Crust
  • OBJECTIVES:
    • Describe the composition of natural gas, petroleum, and coal.
section 22 5 hydrocarbons from earth s crust47
Section 22.5Hydrocarbons From Earth’s Crust
  • OBJECTIVES:
    • Describe what happens when petroleum is refined.
natural gas
Natural Gas
  • Fossil fuels provide much of the world’s energy
  • Natural gas and petroleum contain mostly the aliphatic (or straight-chain) hydrocarbons – formed from marine life buried in sediment of the oceans
  • Natural gas is an important source of alkanes of low molecular mass
natural gas49
Natural Gas
  • Natural gas is typically:
    • 80% methane, 10% ethane, 4% propane, and 2% butane with the remainder being nitrogen and higher molar mass hydrocarbons
    • also contains a small amount of He, and is one of it’s major sources
natural gas50
Natural Gas
  • Natural gas is prized for combustion, because with adequate oxygen, it burns with a hot, clean blue flame:
    • CH4 + 2O2 CO2 + 2H2O + heat
  • Incomplete burning has a yellow flame, due to glowing carbon parts, as well as making carbon monoxide
petroleum
Petroleum
  • The compounds found in petroleum (or crude oil) are more complex than those in natural gas
  • Usually straight-chain and branched-chain alkanes, with some aromatic compounds also
  • Crude oil must be refined (separated) before being used
petroleum52
Petroleum
  • It is separated by distillation into fractions, according to boiling pt.
  • Fractions containing higher molar mass can be “cracked” into more useful shorter chain components, such as gasoline and kerosene
    • involves catalyst and heat
    • starts materials for plastics and paints
slide53
Coal
  • From huge fern trees and mosses decaying millions of years ago under great pressure of rocks / soil.
  • Stages in coal formation:

1. Peat- soft, fibrous material much like decayed garden refuse; high water content. After drying will make a low-cost, smoky fuel

slide54
Coal

2. Lignite- peat left in the ground longer, loses it’s fibrous texture, and is also called brown coal

  • harder than peat; higher C content (50%); still has high water content

3. Bituminous, or soft coal- formed after more time; lower water content, higher C content (70-80%)

slide55
Coal

4. Anthracite, or hard coal

    • carbon content exceeding 80%, making it an excellent fuel source
  • Coal may be found close to the surface (strip-mined), or deep within the earth
  • Pollutants from coal are common; soot and sulfur problems
slide56

BIG BRUTUS

Dragline used to remove the overburden of a strip mining coal field near West Mineral, Kansas.

Note the size of the man standing next to it.

slide57
Coal
  • Coal may be distilled for many products
    • coal gas, coal tar, coke, and ammonia
    • further distilled into benzene, toluene, naphthalene, phenol- the aromatics
    • Coke is almost pure carbon; produces intense heat and little or no smoke, thus used in industrial processes
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