1 CHAPTER 11 An Introduction to Organic Chemistry.
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An Introduction to Organic Chemistry
*Types of Organic CompoundsVast majority of over 20 million known compounds are based on C: organic compounds.Generally contain C and H + other elements (O, N, S, Cl, F, Br, I, P, etc.)Great variety of compounds
*IsomerismIsomers: compounds that have identical composition but different structuresTwo forms of isomerismConstitutional (or structural)StereoisomerismConstitutionalSame empirical formula but different atom-to-atom connectionsStereoisomerismSame atom-to-atom connections but different arrangement in space.
*Stereoisomers: GeometricGeometric isomers can occur when there is a C=C double bond.
*Optical isomers are molecules with non-superimposable mirror images.Such molecules are called CHIRALPairs of chiral molecules are enantiomers.Chiral molecules in solution can rotate the plane of plane polarized light.Stereoisomers: Optical
*Chiral CompoundsPolarized Light
*Stereoisomers IsomersChirality generally occurs when a C atom has 4 different groups attached.Lactic acid
*Alkanes have the general formula CnH2n+2 CH4 = methaneC2H6 = ethaneC3H8 = propaneC4H10 = butaneC5H12 = pentaneHydrocarbons
*Alkanes are colorless gases, liquids, and solidsGenerally unreactive (but undergo combustion)Not polar (or low polarity) and so are not soluble in water.
*Chapter 11 Introduction to Organic Chemistry: Alkanes
10.3 Alkanes with Substituents
*Isomers of ButaneIsomershave the same molecular formula.have different atom arrangements.of butane (C4H10) are a straight chain and a branched chain.
*Alkyl groups Alkyl groups arealkanes that are missing one H. substituents attached to carbon chains.named with a yl ending. H
H C CH3methyl
H H H H C C CH3CH2ethyl H H
*Naming SubstituentsIn the IUPAC system,a carbon branch is named as an alkyl group.halogen atoms are named as halo.TABLE 10.6
*Alkanes with Substituents CH3
CH3 CH CH3 methylpropanemethyl groups CH3 CH3
CH3 CH CH2 CH CH3 2,4-dimethylpentane
*Naming AlkanesGive the name of CH3 CH3 CH3CHCHCH3
STEP 1 Name the longest continuous chain. CH3 CH3 CH3CHCHCH3
*Naming AlkanesGive the name of CH3 CH3 CH3CHCHCH3
STEP 2 Number chain. CH3 CH3 CH3CHCHCH3 1 2 3 4STEP 3 Locate substituents and name. 2,3-dimethylbutane
*Learning CheckWrite the name of
Cl CH3 CH3CH2CHCHCH3
*SolutionSTEP 1 Longest chain is pentane.
STEP 2 Number chain from end nearest substituent. Cl CH3 CH3CH2CHCHCH3 5 4 3 2 1
STEP 3 Locate substituents and name alphabetically. 3-chloro-2-methylpentane
*Learning CheckGive the IUPAC name for each of the following:
A. CH3 CH3 | | CH3CHCH2 CHCH3B. Cl CH3 | |CH3CH2CHCH2CCH2CH3 | Cl
*SolutionA. CH3 CH3 | | CH3CHCH2 CHCH3 2,4-dimethylpentane 1 2 3 4 5B. Cl CH3 more substituents = C3 | |CH3CH2CHCH2CCH2CH3 | Cl 7 6 5 4 3 2 1 3,5-dichloro-3-methylheptane
*Name the following The 6 7 8 longestA. Cl CH2CH2CH3 chain | |CH3CH2CHCH2CCH2CH3 | | Br Cl 1 2 3 4 5 2-bromo-3,5-dichloro-5-ethyloctane
*Learning CheckDraw the condensed structural formula for 2-bromo-4-chlorobutane.
*Solution2-bromo-4-chlorobutaneSTEP 1 Longest chain has 4 carbon atoms.CCCCSTEP 2 Number chain and add substituents. Br Alphabetically: bromo- first than chloro- C C C C Cl 1 2 3 4STEP 3 Add hydrogen to complete 4 bonds to each C. Br CH3CHCH2CH2ClWRONG name! It is 3-bromo-1-chlorobutane
*Naming Cycloalkanes with SubstituentsThe name of a substituent is placed in front of thecycloalkane name.
*Learning CheckName each of the following.
*SolutionName each of the following.
*Chapter 11 Unsaturated Hydrocarbons
11.1 Alkenes and Alkynes
*Saturated hydrocarbonshave the maximum number of hydrogen atoms attached to each carbon atom.are alkanes and cycloalkanes with single C-C bonds.
cyclohexane The cycle is considered as one unsaturationSaturated Hydrocarbons
*Unsaturated hydrocarbonshave fewer hydrogen atoms attached to the carbon chain than alkanes.are alkenes with double bonds.are alkynes with triple bonds. Unsaturated Hydrocarbons
*Bond Angles in Alkenes and AlkynesAccording to VSEPR theory: the three groups bonded to carbon atoms in a double bond are at 120 angles.alkenes are flat because the atoms in a double bond all lie in the same plane.the two groups bonded to each carbon in a triple bond are at 180 angles.
*Naming AlkenesThe names of alkenes CnH2nuse the corresponding alkane name.change the ending to ene.AlkeneIUPACCommonH2C=CH2ethene ethyleneH2C=CHCH3propene propylenecyclohexene
*Ethene (Ethylene)Ethene or ethyleneis an alkene with the formula C2H4. CnH2nhas two carbon atoms connected by a double bond. has two H atoms bonded to each C atom.is flat with all the C and H atoms in the same plane.is used to accelerate the ripening of fruits.
*Naming AlkynesThe names of alkynes CnH2n-2use the corresponding alkane name.change the ending to yne.AlkyneIUPACCommonHCCHethyne acetyleneHCCCH3propyne
*Naming Alkenes and AlkynesWhen the carbon chain of an alkene or alkyne has four or more C atoms, number the chain to give the lowest number to the first carbon in the double or triple bond.CH2=CHCH2CH31-butene 1 2 3 4CH3CH=CHCH32-butene 1 2 3 4 CH3CH2CCCH32-pentyne 5 4 3 2 1
*Learning CheckWrite the IUPAC name for each of the following: 1. CH2=CHCH2CH32. CH3CH=CHCH3 CH3 |3. CH3CH=CCH32-methyl-2-butene 4. CH3CCCH3
*SolutionWrite the IUPAC name for each of the following:
1. CH2=CHCH2CH31-butene2. CH3CH=CHCH32-butene CH3 |3. CH3CH=CCH32-methyl-2-butene 4. CH3CCCH32-butyne
*Learning Check Write the IUPAC name for each of the following:
CH3 B. CH3CH2C=CHCH3
*Solution Write the IUPAC name for each of the following:A. CH3CH2CCCH3 2-pentyne
CH3 B. CH3CH2C=CHCH3 3-methyl-2-pentene
*Cis and Trans IsomersIn an alkene the double bond, is rigid.holds attached groups in fixed positions. makes cis/trans isomers possible.
CH3CH3 CH3 H
C = C C = C H H H CH3 cis trans
*In cis-trans isomersthere is no rotation around the double bond in alkenes.groups attached to the double bond are fixed relative to each other.
You can make a double bond with your fingers with both thumbs on the same side or opposite from each other.Cis-Trans Isomers
*Two isomers are possible whengroups are attached to thedouble bond are different.In a cis isomer, groups are attached on the same side of the double bond.
In the trans isomer, the groups are attached on opposite sides.Cis-Trans Isomers
*Cis-Trans IsomerismAlkenes cannot have cis-trans isomers if a carbon atom in the double bond is attached to identical groups. Identical Identical
2-bromopropene 1,1-dibromoethene (not cis or trans) (not cis or trans)
H H H Br
*Cis-Trans Isomers in NatureInsects emit tiny quantities of pheromones, which are chemicals that send messages.The silkworm moth attracts other moths by emitting bombykol, which has one cis and one trans double bond.
*Naming Cis-Trans Isomers The prefixes cis or trans are placed in front of the alkene name when there are cis-trans isomers. cis
*Learning CheckName each, using cis-trans prefixes when needed.
*Alkenes: Compounds with C=C Double BondsHow many isomers are possible for a compound with the formula C4H8?