Presentation on theme: "Chapter 22 “Hydrocarbon Compounds”"— Presentation transcript:
1 Chapter 22 “Hydrocarbon Compounds” Mr. GowerTroy High School
2 Organic Chemistry and Hydrocarbons “Organic” originally referred to any chemicals that came from organismsGerman chemist Friedrich Wohler synthesized urea in a labToday, organic chemistry is the chemistry of virtually all compounds containing the element carbon
3 Friedrich Wohler1800 – 1882Used inorganic substances to synthesize urea, a carbon compound found in urine.This re-defined organic chemistry.
4 Organic Chemistry and Hydrocarbons Over a million organic compounds, with a dazzling array of propertiesWhy so many? Carbon’s unique bonding ability!Let’s start with the simplest of the organic compounds. These are the Hydrocarbons.
5 Organic Chemistry and Hydrocarbons Hydrocarbons contain only two elements: 1) hydrogen, and 2) carbonsimplest hydrocarbons called “alkanes”, which contain only carbon to carbon single covalent bonds (CnH2n+2)methane (CH4) with one carbon is the simplest alkane. It is the major component of natural gas.
6 Organic Chemistry and Hydrocarbons Review structural formulas - p.694Carbon has 4 valence electrons, thus forms 4 covalent bondsnot only with other elements, but also forms bonds WITH ITSELF (nonpolar)Ethane (C2H6) is the simplest alkane with a carbon to carbon bond
7 Organic Chemistry and Hydrocarbons One carbon atom can form a single covalent bond with four hydrogen atoms.
8 Organic Chemistry and Hydrocarbons Formulas and Models for Methane and EthaneBall-and-stick modelSpace-filling modelDifferent types of formulas and models can be used to represent hydrocarbons such as methane and ethane. Interpreting Diagrams What does a stick in a ball-and-stick model represent?
9 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
10 Alkanes Straight-Chain Alkanes Ethane is the simplest of the straight-chain alkanes, which contain any number of carbon atoms, one after the other, in a chain.
11 Straight-Chain Alkanes Combined with the -ane ending is a prefix for the number of carbons-Table 22.1, page 695Homologous series- a group of compounds that have a constant increment of changeIn alkanes, it is: -CH2- (methylene)
12 AlkanesA group of compounds forms a homologous series if there is a constant increment of change in molecular structure from one compound in the series to the next.
14 Straight-Chain Alkanes Many alkanes used for fuels: methane, propane, butane, octaneAs the number of carbons increases, so does the boiling and melting pt.The first 4 are gases; #5-15 are liquids; higher alkanes are solidsCondensed structural formulas? Note examples on page 696
16 Naming Straight-Chain Alkanes Names recommended by IUPAC - the International Union of Pure and Applied Chemistryend with –ane; the root part of the name indicates the # of carbonsWe sometimes still rely on common names, some of which are well-known
17 Naming Straight-Chain Alkanes IUPAC names may be long and cumbersomeCommon names may be easier or more familiar, but usually do not describe the chemical structure!Methane is natural gas or swamp gas
18 Branched-Chain Alkanes Branched-chain means that other elements besides hydrogen may be attached to the carbonhalogens, oxygen, nitrogen, sulfur, and even other carbonsany atom that takes the place of a hydrogen on a parent hydrocarbon is called a substituent, or the branched part
19 Alkanes Branched-Chain Alkanes An atom or group of atoms that can take the place of a hydrogen atom on a parent hydrocarbon molecule is called a substituent.
20 Branched-Chain Alkanes A hydrocarbon substituent is called an alkyl group or sometimes radicalsuse 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
21 Branched-Chain Alkanes Rules for naming – (go from right to left) - page 6981. Longest C-C chain is parent2. Number so branches have lowest #3. Give position number to branch4. Prefix (di, tri) more than one branch5. Alphabetize branches (not prefix)6. Use proper punctuation ( - and , )
23 Branched-Chain Alkanes From the name, draw the structure, in a right-to-left manner:1. Find the parent, with the -ane2. Number carbons on parent3. Identify substituent groups (give lowest number); attach4. Add remaining hydrogens
27 Alkanes Draw 3-ethylpentane Draw 2,3,4-trimethylhexane Since the electrons are shared equally, the molecule is nonpolarthus, not attracted to wateroil (a hydrocarbon) not soluble in H2O“like dissolves like”
28 22.1 Section Quiz.1. Choose the correct words for the spaces. Because carbon has ______ valence electrons, it can form ______________ bonds.a. four, four covalentb. four, four ionicc. six, six covalentd. six, four or fewer covalent
29 22.1 Section Quiz.2. Alkanes are hydrocarbons that contain only ___________ bonds.a. carbon-carbonb. single covalentc. carbon-hydrogend. ionic
30 22.1 Section Quiz3. Choose the correct words for the spaces. Hydrocarbons are highly soluble in _______ solvents because they are ________ molecules.a. nonpolar, nonpolarb. nonpolar, polarc. polar, nonpolard. polar, polar
31 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=CCalled “unsaturated” if they contain double or triple bonds
32 Naming Alkenes Find longest parent that has the double bond in it New ending: -eneNumber the chain, so that the double bond gets the lower numberName and number the substituentsSamples on page 702
33 AlkenesAlkenes are hydrocarbons that contain one or more carbon-carbon double covalent bonds.
34 AlkenesBecause rotation is restricted around the double bond, atoms in ethene lie in one plane.EtheneBecause rotation is restricted around the double bond, atoms in ethene lie in one plane. Calculating What is the ratio of hydrogen to carbon in ethene?
35 AlkynesHydrocarbons containing carbon to carbon triple bonds are called alkynes(CnH2n-2) C C-Alkynes are not plentiful in natureSimplest is ethyne- common name acetylene (fuel for torches)Table 22.3, p. 703 for boiling pt.ethyne
36 AlkynesAt least one carbon-carbon bond in an alkyne is a triple covalent bond. Other bonds may be single or double carbon-carbon bonds and single carbon-hydrogen bonds.
37 Alkynes Alkenes and alkynes are unsaturated! Straight-chain and branched-chain alkanes, alkenes, and alkynes are aliphatic hydrocarbons.
39 AlkynesThe triple bond restricts rotation in an ethyne molecule, which has a linear shape.The triple bond restricts rotation in an ethyne molecule, which has a linear shape. Calculating What is the ratio of hydrogen to carbon in ethyne?
40 22.2 Section Quiz.1. Alkenes and alkynes are called unsaturated compounds because they containa. single bonds only.b. double or triple bonds.c. oxygen atoms.d. hydrogen atoms.
41 22.2 Section Quiz.2. What is the correct name for a compound with a C-C-C=C-C carbon skeleton?a. 3-pentyneb. 2-pentenec. 3-pentened. 4-pentene
42 22.2 Section Quiz. 3. Which of the following substances is an alkyne? a. C6H12b. C2H4c. C2H2d. C4H8
43 Structural IsomersCompounds that have the same molecular formula, but different molecular structures, are called structural isomersButane 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
45 StereoisomersDon’t forget that these structures are really 3-dimensionalstereoisomers- 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
46 Geometric IsomersThere is a lack of rotation around a carbon to carbon multiple bondhas an important structural implicationTwo possible arrangements:1. trans configuration - substituted groups on opposite sides of double bond2. cis configuration - same side
47 Geometric IsomersSubstituted groups are on opposite sides of the double bond (in this case, one is above, the other is below)Trans-2-buteneSubstituted groups are on the same side of the double bond (in this case, both are above)Cis-2-butene
48 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)
49 Geometric IsomersIn the trans configuration, the methyl groups are on opposite sides of the double bond.In the cis configuration, the methyl groups are on the same side of the double bond.
50 Optical IsomersAsymmetric carbon? C with 4 different groups attached. Conceptual Problem 22.4, p.706Molecules containing asymmetric carbons have “handedness”, and exist as stereoisomers.Figure 22.9, page 705
51 Optical Isomers, and these will each show an asymetric carbon (4 different branches attached) The asymetric carbon
54 22.3 Section Quiz1. Structural isomers have different properties because they havea. a different number of bonds.b. different types of bonds.c. different substituents.d. a different order of atoms.
55 22.3 Section Quiz2. Substituent groups on opposite sides of a double bond are said to be in the _______ configuration. If the groups are on the same side of the bond, then they are in the _______ configuration.a. cis, transb. trans, cisc. trans, isod. stereo, cis
56 22.3 Section Quiz3. Geometric isomers have different arrangements of atomsa. and different molecular formulas.b. but only single bonds.c. around an asymetric carbon.d. around a double bond.
57 22.3 Section Quiz4. A carbon atom that has four different substituents always formsa. an optical isomer.b. a saturated hydrocarbon.c. a geometric isomer.d. an unsaturated hydrocarbon.
58 Cyclic HydrocarbonsThe two ends of the carbon chain are attached in a ring in a cyclic hydrocarbonsample drawings on page 709named as “cyclo- ____”hydrocarbon compounds that do NOT contain rings are known as aliphatic compounds
59 Cyclic Hydrocarbons Three Ways to Represent Cyclic Hydrocarbons The simplest cyclic hydrocarbon has a 3-carbon ring. Rings containing up to 20 carbon atoms are found in nature. Rings with 5 or 6 carbons are the most abundant.
60 Aromatic Hydrocarbons A special group of unsaturated cyclic hydrocarbons is known as arenescontain single rings, or groups of ringsalso called “aromatic hydrocarbons”, because of pleasant odorsimplest aromatic is benzene (C6H6)Term “aromatic” applies to materials with bonding like that of benzene
61 Aromatic Hydrocarbons Benzene is a six-carbon ring, with alternating double and single bondsexhibits resonance, due to location of the double and single bonds-p.710Benzene derivatives possible:methylbenzene, 3-phenylhexane, ethylbenzene (top page 711)
62 Aromatic Hydrocarbons The Structure of BenzeneBenzene can be shown as switching, or resonating, between two arrangements of alternating double and single bonds.
63 Aromatic Hydrocarbons The three symbols below can be used to represent the benzene ring. If the bonds are shown as alternating single and double bonds (on right), it is important to remember that bonds don’t actually alternate and that all six bonds are identical.
64 Aromatic Hydrocarbons Space-filling Model of BenzeneThis is a space-filling model of benzene. Applying Concepts What is the molecular formula of benzene?
65 Aromatic Hydrocarbons Substituted Aromatic CompoundsCompounds with a substituent on a benzene ring are named as a derivative of benzene. When benzene is a substituent, it is called a phenyl group.
66 Aromatic Hydrocarbons A benzene ring can have two or more substituents.
67 Aromatic Hydrocarbons The molecules of many dyes include benzene rings.The molecules of many dyes include benzene rings. Dyes that contain aromatic compounds are called aniline dyes.
68 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”CH2CH
69 Aromatic Hydrocarbons Benzene derivatives can have two or more substitutents:1,2-dimethylbenzene1,3-dimethylbenzene1,4-dimethylbenzeneCan use ortho for 1,2; meta for 1,3; and para for 1,4 (page 711)CCCC
70 22.4 Section Quiz.1. Choose the correct words for the spaces. Alkanes that do not contain a ring structure are _______ hydrocarbons. Alkanes that do contain ring structures are called _________ hydrocarbons.a. aliphatic, aromaticb. aromatic, aliphaticc. aliphatic, cyclicd. aromatic, cyclic
71 22.4 Section Quiz.2. The carbon-carbon bonds in a benzene molecule area. alternating double and single bonds.b. identical hybrid bonds.c. all double bonds.d. all single bonds.
72 22.4 Section Quiz.3. When an alkane has a benzene ring as a substituent, the ring is called _______ group.a. a benzeneb. a toluenec. a phenyld. an arene
73 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 oceansNatural gas is an important source of alkanes of low molecular mass
74 Natural Gas Natural gas is typically: 80% methane, 10% ethane, 4% propane, and 2% butane with the remainder being nitrogen and higher molar mass hydrocarbonsalso contains a small amount of He, and is one of it’s major sources
75 Natural GasNatural gas is prized for combustion, because with adequate oxygen, it burns with a hot, clean blue flame:CH4 + 2O CO2 + 2H2O + heatIncomplete burning has a yellow flame, due to glowing carbon parts, as well as making carbon monoxide
76 PetroleumThe compounds found in petroleum (or crude oil) are more complex than those in natural gasUsually straight-chain and branched-chain alkanes, with some aromatic compounds alsoCrude oil must be refined (separated) before being used
77 PetroleumIt 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 keroseneinvolves catalyst and heatstarts materials for plastics and paints
78 Natural Gas Wells are drilled to reach natural gas and petroleum. 22.5 Wells are drilled to reach natural gas and petroleum. Pressure from the trapped gas may force petroleum up a well pipe, but pumping is usually required.
79 22.5PetroleumIn fractional distillation, the crude oil is heated so that it vaporizes and rises through the fractionating column. The column is hotter at the bottom and cooler at the top.In fractional distillation, the crude oil is heated so that it vaporizes and rises through the fractionating column. The column is hotter at the bottom and cooler at the top. Compounds with the highest boiling points condense near the bottom. Compounds with the lowest boiling points condense near the top.
81 CoalFrom 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
82 Coal2. Lignite- peat left in the ground longer, loses it’s fibrous texture, and is also called brown coalharder than peat; higher C content (50%); still has high water content3. Bituminous, or soft coal- formed after more time; lower water content, higher C content (70-80%)
83 Coal 4. Anthracite, or hard coal carbon content exceeding 80%, making it an excellent fuel sourceCoal may be found close to the surface (strip-mined), or deep within the earthPollutants from coal are common; soot and sulfur problems
84 22.5CoalCoal FormationCoal formed when tree ferns and mosses died and were subjected to continued pressure and heat underground.Coal formed when tree ferns and mosses died. The layers of decaying organic material were compressed over millions of years between layers of soil and rock. The first stage in coal formation is peat. Continued pressure and heat transform peat into lignite, bituminous coal, and anthracite coal.
85 22.5CoalCoal consists largely of condensed aromatic compounds of extremely high molar mass. These compounds have a high proportion of carbon compared with hydrogen.
86 Coal Coal is mined from both surface mines and underground mines. 22.5 Coal is mined from both surface mines, shown here, and underground mines.
87 Note the size of the man standing next to it. BIG BRUTUSDragline 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.
88 Coal Coal may be distilled for many products coal gas, coal tar, coke, and ammoniafurther distilled into benzene, toluene, naphthalene, phenol- the aromaticsCoke is almost pure carbon; produces intense heat and little or no smoke, thus used in industrial processes