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1 “WE R FAMILY” Functional groups determine the family a substance is in. They also determine how that substance is names and it properties 2 3 22.4 Hydrocarbon Rings> Cyclic Hydrocarbons A compound that contains a hydrocarbon ring is called a cyclic hydrocarbon. 4 • Many molecules found in nature contain cyclic hydrocarbons. • Rings with five and six carbons are the most abundant. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 22.4 Hydrocarbon Rings> Cyclic Hydrocarbons • Just as straight-chain and branched-chain alkanes can be either saturated or unsaturated, so can cyclic hydrocarbons. • A cyclic hydrocarbon that contains only single bonds, and is therefore saturated is called a cycloalkane. 5 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 22.4 Hydrocarbon Rings> Cyclic Hydrocarbons • To determine the IUPAC name of a cycloalkane, first count the number of carbons in the ring and assign the corresponding alkane name. Name: cyclopropane 6 • Then simply add the prefix cyclo- to the alkane name. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Benzene • • • has six electrons shared equally among six carbon atoms in a ring is written as two possible ring structures is also represented as a hexagon with a circle drawn inside 7 Basic Chemistry Copyright © 2011 Pearson Education, Inc. 8 Resonance in Benzene • C6H6 has two resonance structures with alternating double bonds. • The π electrons are delocalized over the ring. H C H C C H HC C C H H H H C C H C C H CH C H Resonance structures of benzene, C6 H6 H C H C C H HC C C H H Abbreviated representation of resonance structures 9 Resonance in Benzene • CC bond order is _______________ • C–C single bond = 154 pm C=C bond = 134 pm • CC bonds in benzene = 139 pm π electrons delocalized 22.4 Hydrocarbon Rings> Aromatic Hydrocarbons Substituted Aromatic Rings • Compounds containing substituents attached to a benzene ring are named using benzene as the parent hydrocarbon. 10 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 22.4 Hydrocarbon Rings> Aromatic Hydrocarbons Substituted Aromatic Rings When the benzene ring is a substituent, the C6H5 group is called a phenyl group. 11 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 12 Benzene Derivatives Aniline C6H5NH2 Phenol C6H5OH TNT trinitrotoluene C6H4CH3(NO2)3 Aromatic Compounds in Nature and Health 13 Basic Chemistry Copyright © 2011 Pearson Education, Inc. Aromatic compounds are named • with benzene as the parent chain • with the name of a substituent in front of the name benzene • with common names for some substituted compounds 14 Basic Chemistry Copyright © 2011 Pearson Education, Inc. Naming Aromatic Compounds When two groups are attached to benzene, the ring is numbered to give the lower number to the side group. 15 Basic Chemistry Copyright © 2011 Pearson Education, Inc. Example of Naming an Aromatic Compound Select the correct name for the following structure: 1) chlorohexane 2) 2) chlorobenzene chlorobenzene 3) 1-chlorobenzene 16 Basic Chemistry Copyright © 2011 Pearson Education, Inc. Write the IUPAC name of the following compound: CH3 STEP 1 Write the name of the aromatic compound. benzene Cl STEP 2 Number the aromatic ring starting from the substituent. The ring is numbered to give the lower number to the methyl substituent. CH3 STEP 3 Give the location and name of each substituent as a prefix to the name. 3-chloromethylbenzene 17 Basic Chemistry Copyright © 2011 Pearson Education, Inc. 1 2 3 Cl Draw the condensed structural formula for 1-bromo-3,4-dichlorobenzene. The name indicates a benzene ring with one bromine atom and two chlorine atoms. Counting the carbon attached to the bromine atom as carbon 1, the chlorine atoms are attached to carbons 3 and 4. Br Cl Cl 18 Basic Chemistry Copyright © 2011 Pearson Education, Inc. 22.4 Hydrocarbon Rings> Aromatic Hydrocarbons Substituted Aromatic Rings • There are three constitutional isomers for dimthylbenzene (C6H4(CH3)2). • The boiling points of the three compounds are a reminder that constitutional isomers have different physical properties. 19 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 22.4 Hydrocarbon Rings> Aromatic Hydrocarbons Substituted Aromatic Rings • In the IUPAC naming system, the possible positions of two substituents in disubstituted benzene are designated as 1,2; 1,3; or 1,4. • Common names for disubstituted benzenes use the terms ortho, meta, and para (abbreviated as o, m, and p) in place of numbers. 20 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Naming Benzene Derivatives Cl 1 6 2 3 5 4 Ortho to Cl Meta to Cl Para to Cl 1,4-dimethylbenzene Common name: Para-xylene 21 22 Simple ORGANIC Reactions COMBUSTION ADDITION REACTIONS ESTERIFICATION SUBSTITUTION Substitution Reactions 24 Reactions of Aromatics • Substitutions — not additions — are typical. CH3 + CH3Cl AlCl3 AlCl3 is a catalyst. + HCl Addition Reactions 26 Reactions of Alkenes: ADDITION REACTIONS • Alkenes are unsaturated — more bonds can form to the C atoms • Molecules such as Br2, H2, HCl, HBr, and H2O add to the double bond H C C + Br2 H H H Br Br H C C H H H 1,2-dibromoethane An Addition Reaction • Fats can be “hydrogenated” with H2. Peanut butter has partially hydrogenated vegetable oil. 27 H2 C HC H2 C O O CR O O CR O O CR 28 Fats and Oils Fats with C=C bonds are usually LIQUDS Oleic acid: a monounsaturated fatty acid C=C bond H2 C HC H2 C O O CR O O CR O O CR 29 Fats and Oils Fats with saturated acids (no C=C bonds) are SOLIDS. Saturated fats are more common in animals. 30 Fats H2 C HC H2 C O O CR O O CR O O CR What is the functional group in a fat or oil? R = organic group with NO C=C bonds C12 = Lauric acid C16 = Palmitic acid C18 = Stearic acid R = organic group with C=C bonds C18 = oleic acid Esterification 32 Acids + Alcohols --> ESTERS Esters have generally pleasant odors 33 Acids + Alcohols --> ESTERS O O CH 3COH + CH 3CH 2OH Acetic acid H+ CH 3COCH 2CH 3 + H 2O Ethyl acetate Ethanol O O RC—O—H + R'—O—H Carboxylic acid Alcohol H+ RC—O—R' + H 2O Ester One of the important reactions in nature! 34 Acids + Alcohols --> ESTERS 3-methylbutanol Acetic acid O H 3C C CH3 O CH2 CH2CHCH3 3-methylbutylacetate Combustion C S E A A C A E A S