Chapter 23: Organic Chemistry, Polymers, and Biochemicals Chemistry: The Molecular Nature of Matter, 6E Jespersen/Brady/Hyslop
Carbon Chemistry Bonding • Strong covalent bonding to itself and to other non-metal elements • Capable of forming extremely long carbon-carbon chains • Multiple arrangements of identical molecular formulas lead to numerous isomers.
Structural Formula Representations Lewis Structure of Pentane Condensed Structural Formula • CH3CH2CH2CH2CH3 pentane
Structural Formula Representations • Lewis Structure of Pentan-1-ol • Condensed Structural Formula CH3CH2CH2CH2CH2OH 1-pentanol
Chiral Isomers of Carbon Chirality exists when carbon has four unique constituents bond to itself | | | | | Non-superimposable mirror images
Abbreviated or Bond-Line Structure Carbon atoms occur at intersection but no symbol used CH3–CH2–CH3 would appear as: Non-carbon atoms would appear as symbols CH3–CH2–CH2–OH would appear as:
Abbreviated or Bond-Line StructureOpen-Chain Compounds Examples butane-1-ol butane
Abbreviated or Bond-Line Structure of Ring Compounds Chair Form of Cylcohexane Cyclohexane Cyclopropane Benzene
Abbreviated or Bond-Line Structure Heterocyclic Compounds Piperazine Pyridine Pyrazole Furan Tetrahydropyran
Learning Check 1. Draw at least two geometric isomers of C4H10 using abbreviated structures. 1. Draw the four carbon chain first 2. Now rearrange CH3 groups
Your Turn! When a chemical formula is written in the following form, CH3CH2CH2COOH, the representation is known as • an abbreviated structure • a Lewis dot structure • a condensed formula • an optical isomer
Functional Groups in Organic • Organic families can be defined by functional groups. • Frequently use “R” as a place holder for alkane-like hydrocarbon groups R–OH alcohol R–COOH organic acid R–O–R’ ether
Learning Check 1. Write the abbreviated structure for benzoic acid. 2. What family does C6H5NH2 belong to? 1. 2. amine family
Your Turn! Which of the following is an example of an ester? • CH3CH2CH2OH B. C. D.
Hydrocarbons • Hydrocarbon compounds only contain C and H • Alkanes CnH2n+2 CH3CH2CH3 propane • Alkenes CnH2n CH3CHCH2 propene • Alkynes CnH2n-2 CH3CCH propyne • Aromatic C6H6 benzene • Characterized by cyclic delocalized πbonding
Hydrocarbons • Alkanesare defined as saturated compounds. • All singles bond to carbon • Cannot add more hydrogen atoms • Alkenesand alkynesare unsaturated compounds. • Alkenes have double bonds and H atoms can be added to the double bond to create a saturated compound. • Alkynes have triple bonds and H atoms can be added to create a saturated compound. • CH2=CHCH3 + H2CH3CH2CH3
Aromaticity • Characterized by conjugated bonds in a ring such as benzene. • π electrons are delocalized over the ring • Leads to greater stability than expected • Properties are different than those of other hydrocarbon families • Polycyclic examples:
Hydrocarbon Nomenclature Rules for naming alkanes Established by IUPAC 1. Name ends in “-ane” 2. Complete name uses that of parent compound with constituent groups added. 3. Parent is longest continuous carbon chain. 4. Name of longest chain based on the number of carbons. 5. Carbon atoms are numbered starting at the end that gives the lowest number for the first branch.
Alkyl Groups Alkane type groups added to parent chain are known as alkyl groups. Consist of alkane, minus one H atom. Name always ends in –yl Example CH4 : now remove one H which yields –CH3 • Naming of –CH3 • Start with parent name, which is methane • Drop –ane and add –yl • So methane becomes methyl group
Alkyl Groups • CH3CH2CH3 yields –CH2CH2CH3 when one H atom is removed from the end carbon. • The name of the aryl group is propyl. • Note, you can have another isomer of propyl. • The other isomer’s aryl group is 1-methylethyl, or isopropyl, and is created when the H atom is removed from the non-terminal carbon.
Nomenclature 6. Aryl groups names are prefixed to parent name. 7. Multiple aryl groups on a parent are numbered and named alphabetically. 8. When there are multiple identical groups add di, tri, tetra to the aryl name. 9. If multiple, identical aryl groups are attached to the same carbon repeat the carbon number.
Examples What is the name of the compound shown? • The longest carbon chain (parent) is four. Parent name is butane. • Start numbering from the left to get the smallest number for the attached group.
Examples 3. The attached alkyl group is a methyl group. • Thus, the correct name is: • 2-methylbutane • What is the name of the following compound?
Examples • The parent chain contains five carbons. • Thus, the parent name is pentane. • Number from the left to obtain the smallest number for the first alkyl group. • The alkyl groups are at the 2 and 3 positions. • The 2 and 3 positions each contain a methyl group.
Examples • Thus, the correct name is: • 2,3-dimethylpentane • Let’s consider an alkane with two substituents on the same carbon.
Examples • The parent chain is six carbons long. • The lowest correct numbering of positions is shown below. • There are methyl and ethyl groups attached to carbon 3.
Examples • The correct name is: 3-ethyl-3-methylhexane
Your Turn! What is the correct name for the molecule shown below? A. 3-butylpentane B. 1,1-diethylpentane C. 3-ethylheptane D. 5-ethylheptane
Your Turn! What is the name of the compound shown below? A. 3-methyl-3-methyloctane B. 3,3-dimethyloctane C. 2-ethyl-2-methylheptane D. 6,6-dimethyloctane
Chemical Properties of Alkanes • Alkanes are relatively unreactive • Not reactive in conc. NaOH or H2SO4 at room temperature. • React with hotHNO3 • Will react with Cl2 and Br2 to form halogenated hydrocarbons. • Examples are CH3Cl, CH2Cl2 and CHCl3 • Can crack molecules like ethane under controlled conditions to form CH2CH2 • Will react with O2 to form CO2, CO, and H2O
Alkenes and Alkynes • Alkenes contain one or more double bonds • General form: CnH2n • Alkynes contain one or more triple bonds • General form: CnH2n-2 • Non-polar compounds are not water soluble • Examples: Ethene or ethylene Ethyne or acetylene
Alkenes and Alkynes • Nomenclature • The parent chain must contain the multiple bond even if it is a smaller chain length than one without a multiple bond • Number from end that gives the lowest number to the first carbon of the multiple bond • The number is given as -x- and placed just before the –ene or –yne of the parent name. • For example, but-2-ene. The double bond starts on carbon 2 of the chain.
Alkene Examples • Start numbering from the left to get the lowest number for the first carbon with the double bond • The parent is heptene and the correct naming including the double bond location would be hep-2-ene
Alkene Example • The parent chain is four carbons • 2,3-dimethylbut-2-ene • We would not name this 2-methyl-3-methylbut-2-ene
Naming Polyenes • How do we name compounds such as the following? • This compound contains two double bonds and is known as a diene • We want the lowest number for the first carbon of each of the double bonds • Start numbering from the right
Naming Polyenes • The correct name would be hex-1,3-diene • Three double bonds would be a triene hex-1,3,5-triene
Cyclic Alkenes • Number ring to obtain lowest number for first carbon of the double bond
Cyclic Alkenes • Correct name is 1,6-dimethylcyclohex-1-ene • Other ring examples Cyclooctene Cyclopentene
Your Turn! What is the correct name for the compound shown below? A. 1,4-dimethylcyclopent-1-ene B. 1,3-dimethylcyclopent-1-ene C. 1-methyl-4-methylcyclopent-1-ene D. 1,3-dimethylcyclo-1-pentene
Your Turn! What is the correct structure for 3,3-dimethylpro-1-ene? A. B. C. D.
Geometric Isomers • Groups cannot freely rotate about a double bond • Therefore, it is possible to have geometric isomers • Examples: trans-1,2-dibromoethene cis-1,2-dibromoethene
Reactions of Alkene • Alkenes readily add across the double bond • Examples of an addition reaction: • CH2CH2 + H2 CH3CH3 hydrogenation • CH2CH2 + HCl → CH3CH2Cl • CH2CH2 + H2O → CH3CH2OH • CH2CH2 + Cl2→ CH2ClCH2Cl
Aromatic Hydrocarbons • The most common aromatic compound is benzene and its derivatives • Representation of bonding • Delocalized πbonds create unique stability, called resonance stabilization. The circle in the ring represents delocalization.
Reactions • Substitution reactions maintain benzene’s resonance structure. • Addition reactions, like those of alkenes, destroy resonance structure • Substitution reaction:
Addition Reaction • Notice that you have reduced the double bonding in the ring and altered the resonance stabilization of the ring
Learning Check: What product would form if benzene reacted with nitric acid using an appropriate catalyst? • Sulfuric acid is the catalyst • A substitution reaction occurs
Your Turn! Which product is most likely formed when sulfuric acid reacts with benzene? A. B. C. D.