Introduction to Organic Chemistry

Common Elements in Organic Compounds 24.1

Classification of Hydrocarbons 24.1

Classification of Hydrocarbons Aliphatic: Relating to or denoting organic compounds in which carbon atoms form open chains 24.1

Classification of Hydrocarbons Aromatic: a hydrocarbon that contains one or more benzene rings. 24.1

CH4 C2H6 C3H8 methane ethane propane Alkanes have the general formula CnH2n+2 where n = 1,2,3,… alkanes have only single covalent bonds alkanes are called saturated hydrocarbons because they contain the maximum number of hydrogen atoms that can bond with the number of carbon atoms in the molecule. (unsaturated hydrocarbons = alkenes & alkynes) CH4 C2H6 C3H8 methane ethane propane 24.2

Structural isomers are molecules that have the same molecular formula but different structures 24.2

How many structural isomers does pentane, C5H12, have? n-pentane C H CH3 2,2-dimethylpropane 2-methylbutane 24.2

Alkane Nomenclature The parent name of the hydrocarbon is that given to the longest continuous chain of carbon atoms in the molecule. CH3 CH2 CH 4-methylheptane 1 2 3 4 5 6 7 An alkane less one hydrogen atom is an alkyl group. CH4 methane CH3 methyl 24.2

1 Meth; 2 Eth; 3 Prop; 4 But; 5 Pent Alkane Nomenclature 1 Meth; 2 Eth; 3 Prop; 4 But; 5 Pent 6 Hex; 7 Hept; 8 Oct; 9 Non; 10 Dec 24.2

Alkane Nomenclature Names of Common Substituent Groups Functional Group Name -NH2 amino -F fluoro -Cl chloro -Br bromo -I iodo -NO2 nitro -OH alcohol

When one or more hydrogen atoms are replaced by other groups, the name of the compound must indicate the locations of carbon atoms where replacements are made. Number in the direction that gives the smaller numbers for the locations of the branches. CH3 CH CH2 1 2 3 4 5 CH3 CH2 CH 2-methylpentane 1 2 3 4 5 4-methylpentane 24.2

When one or more hydrogen atoms are replaced by other groups, the name of the compound must indicate the locations of carbon atoms where replacements are made. Number in the direction that gives the smaller numbers for the locations of the branches. CH3 CH CH2 1 2 3 4 5 CH3 CH2 CH 2-methylpentane 5 4 3 2 1 2-methylpentane 24.2

When one or more hydrogen atoms are replaced by other groups, the name of the compound must indicate the locations of carbon atoms where replacements are made. Number in the direction that gives the smaller numbers for the locations of the branches. CH3 CH CH2 1 2 3 4 5 CH3 CH2 CH 2-methylpentane 1 2 3 4 5 4-methylpentane 24.2

Alkane Nomenclature Prefixes: di means double tri means triple Use prefixes di-, tri-, tetra-, when there is more than one alkyl branch of the same kind. CH3 CH CH2 1 2 3 4 5 6 2,3-dimethylhexane CH3 CH2 C 1 2 3 4 5 6 Prefixes: di means double tri means triple tetra means quadruple 3,3-dimethylhexane 24.2

Use previous rules for other types of substituents. Alkane Nomenclature Use previous rules for other types of substituents. CH3 CH Br 1 2 3 4 Cl Names of Common Substituent Groups Functional Group Name -NH2 amino -F fluoro -Cl chloro -Br bromo -I iodo -NO2 nitro -OH alcohol 2-bromo-3-chlorobutane CH2 CH CH3 Br 1 2 3 4 F 1-bromo-3-fluorobutane 24.2

Yes, the groups (branches) need to be listed alphabetical! What is the IUPAC name of the following compound? methyl branch ethyl branch CH3 CH CH2 CH2CH3 1 2 3 4 5 6 7 8 …octane 4-ethyl-2-methyl-octane Yes, the groups (branches) need to be listed alphabetical! What is the structure of 2-chloro-4-methylhexane? CH3 CH CH2 Cl 1 2 3 4 5 6 24.2

Summary of naming rules: 1) Assign a parent name based upon the longest continuous Carbon chain.(Find the longest chain) 2) Identify the branches off the parent chain. 3) Same groups in different places? Use prefixes. (di for two, tri for three, or tetra for four) 4) Assign location numbers (called locants) to all of the groups. Count along the parent chain in both directions: use the version that yields the lowest starting locant for a branch. 5) Shove it all together alphabetically using commas and dashes!

Practice Makes Perfect! Let’s build this model then name it. CH3 CH CH2 Br 6 5 4 3 2 1 Locants 3-bromo-2,4-dimethylhexane Br 6 5 4 3 2 1 Locants 3-bromo-2,4-dimethylhexane

Practice Makes Perfect! Let’s build this model then name it. CH3 CH CH2 Br 6 5 4 3 2 1 Locants 3-bromo-2,4-dimethylhexane Br Cl 9 8 7 6 5 4 3 2 1 Locants 6-bromo-7-chloro-2-methylnonane

Draw 2-bromo-4-ethyl-3-methylheptane Draw 1-chloro-4,4-diethyloctane

Optical Isomers achiral chiral 24.2

Build these models: CH2BrCl CHBrClF

not not superimposable on its mirror image video achiral chiral 24.2

In the 1960’s, a drug called thalidomide was widely prescribed in the Western Europe to alleviate morning sickness in pregnant women. effective medication causes birth defects

Alkanes whose carbon atoms are joined in rings are called cycloalkanes Alkanes whose carbon atoms are joined in rings are called cycloalkanes. They have the general formula CnH2n where n = 3,4,… 24.2

Alkenes have the general formula CnH2n contain at least one carbon-carbon double bond also called olefins CH2 CH CH3 CH3 CH 1-butene 2-butene C Cl H C Cl H cis-dichloroethylene trans-dichloroethylene 24.2

CH2 CH3 CH 1-hexene CH2 CH3 CH 2-hexene CH2 CH3 CH 2-hexene

Alkynes have the general formula CnH2n-2 contain at least one carbon-carbon triple bond CH3 C CH C CH2 CH3 1-butyne 2-butyne 24.2

Aromatic Hydrocarbons 24.3

Aromatic Compound Nomenclature CH2CH3 ethylbenzene NH2 aminobenzene Cl chlorobenzene NO2 nitrobenzene Br Br 1 2 3 4 5 6 1,2-dibromobenzene 1,3-dibromobenzene 24.3

Aromatic Compound Reactions Substitution reaction H Br + HBr + Br2 FeBr3 catalyst H CH2CH3 + HCl + CH3CH2Cl AlCl3 catalyst 24.3

Polycyclic Aromatic Hydrocarbons 24.3

Functional Group Chemistry Alcohols contain the hydroxyl functional group and have the general formula R-OH. 24.4

Functional Group Chemistry Ethers have the general formula R-O-R’. Condensation Reaction CH3OH + HOCH3 CH3OCH3 + H2O H2SO4 catalyst 24.4

Functional Group Chemistry Carboxylic acids contain the carboxyl ( -COOH ) functional group. 24.4

Functional Group Chemistry Esters have the general formula R’COOR, where R is a hydrocarbon group. CH3COOH + HOCH2CH3 CH3 C O CH2CH3 + H2O O ethyl acetate 24.4

Functional Group Chemistry Amines are organic bases with the general formula R3N. CH3NH2 + H2O RNH3+ + OH- CH3CH2NH2 + HCl CH3CH2NH3+Cl- 24.4

24.4

Chemistry In Action: The Petroleum Industry Crude Oil

1 meth 2 eth 3 prop 4 but 5 pent 6 hex 7 hept 8 oct 9 non 10 dec Alkane – single bonds Alkene – double bonds Alkyne – triple bonds Cyclo – chained ring Benzene – special ring