1/31/18 CHEM 109A Organic Chemistry https://labs.chem.ucsb.edu/zakarian/armen/courses.html Chapter 3 An Introduction to Organic Compounds Nomenclature, Physical Properties, and Structure © 2017 Pearson Education, Inc. How many hydrogens are attached to each carbon HO cholesterol © 2017 Pearson Education, Inc. 1 1/31/18 Alkanes are Saturated Hydrocarbons, CnH2n+2, Only Single Bonds heating power bbq lighters gasoline jet fuel diesel © 2017 Pearson Education, Inc. Types of Alkanes in Chapter 3 straight chain branched cyclic (CnH2n+2) (C H ) n 2n+2 (CnH2n) hexane cyclohexane butane © 2017 Pearson Education, Inc. 2 1/31/18 Alkanes and Alkyl Groups: Two alkanes C4H10 CH3CH2CH2CH2−X X Butane Butyl group and X X CH3CH2CH2CH3 CH3CH2CHCH2 Butane sec-butyl group and Isobutane X CH3CH(CH3)2 X and CH3 (CH3)3C−X CH3 CH (CH3)2CHCH2−X CH3 Isobutane isobutyl group tert-butyl group © 2017 Pearsonbutane Education, Inc. and isobutane are constitutional isomers Alkyl Substituents X X X X ethyl group n-propyl group n-butyl group n-pentyl group R X generic alkyl group © 2017 Pearson Education, Inc. 3 1/31/18 n = an Unbranched Chain Common names sometimes use “n” (stands for “normal”) to indicate a straight-chain alkane. © 2017 Pearson Education, Inc. Alkyl Substituents X X X X ethyl group n-propyl group n-butyl group n-pentyl group X R X X sec-butyl group isobutyl group generic alkyl group branched alkyl groups © 2017 Pearson Education, Inc. 4 1/31/18 Primary, Secondary, and Tertiary Carbons • A primary carbon is bonded to one carbon. • A secondary carbon is bonded to two carbons. • A tertiary carbon is bonded to three carbons. • Primary hydrogens are attached to primary carbons. • Secondary hydrogens are attached to secondary carbons. • Tertiary hydrogens are attached to tertiary carbons. © 2017 Pearson Education, Inc. Common Types of Organic Compounds R N R R O R X R OH R NH2 H R R N X = F, or Cl, or Br, or I R R an alkyl halide an alcohol an ether an alkyl amine © 2017 Pearson Education, Inc. 5 1/31/18 Nomenclature: Systematic and Common Summary of basic rules for systematic nomenclature: 1. find the longest carbon chain: that is your root (8 carbons? - octane....) 2. number the carbons – start with the end closest to a substituent or branching point 3. properly name the substituent alkyl groups: name the group, goes in front as prefix, alphabetical order halides: fluoro-, chloro-, bromo-, iodo-, if more than 1, di(bromo)-, tri-, tetra-, etc. also go in front, alphabetical order HO groups: back of the name (suffix), -ol (like methanol); if more than one, -diol, -triol, -tetraol..... RO groups: called alkoxy- (methoxy, ethoxy, etc.) go in front NH2 groups: go in the back as -amine (1-butanamine) © 2017 Pearson Education, Inc. sec-Pentyl is Not a Good Name A name must specify only one compound. © 2017 Pearson Education, Inc. 6 1/31/18 “tert” Can Be Used with “Butyl” and “Pentyl” tert-hexyl is not a good name. © 2017 Pearson Education, Inc. “Iso” Iso is at one end, and the group replacing the H is at the other end. © 2017 Pearson Education, Inc. 7 1/31/18 Alkyl Group Names © 2017 Pearson Education, Inc. Nomenclature of Alkanes First identify the longest continuous chain (the parent hydrocarbon) © 2017 Pearson Education, Inc. 8 1/31/18 Add the Name of the Substituent Number the chain in the direction that gives the substituent as low a number as possible. © 2017 Pearson Education, Inc. Common versus Systematic Nomenclature Common names never have numbers. Only systematic names have numbers. © 2017 Pearson Education, Inc. 9 1/31/18 List Substituents in Alphabetical Order The correct name is the one that contains the lowest number. © 2017 Pearson Education, Inc. Multiple Substituents The chain is numbered in the direction that puts the lowest number in the name. Substituents are listed in alphabetical order. (di, tri, tetra, sec, tert are not alphabetized) © 2017 Pearson Education, Inc. 10 1/31/18 When Both Have the Same Lowest Number When both names have the same lowest number, go for the next lowest number. © 2017 Pearson Education, Inc. When Both Have the Same Numbers When the same numbers are obtained in both directions, the first group listed gets the lower number. © 2017 Pearson Education, Inc. 11 1/31/18 Branched Substituents If the substituent has a common name, the common name can be used instead of the parenthetical name. © 2017 Pearson Education, Inc. Branched Substituents If the substituent does not have a common name, the parenthetical name has to be used. © 2017 Pearson Education, Inc. 12 1/31/18 Chains with the Same Length When two or more chains have the same length, the parent hydrocarbon is the chain with the most substituents. © 2017 Pearson Education, Inc. Cycloalkanes Skeletal structures do not show Cs and Hs bonded to Cs. © 2017 Pearson Education, Inc. 13 1/31/18 Monosubstituted Cycloalkanes A number is not needed. © 2017 Pearson Education, Inc. Disubstituted Cycloalkanes Substituents are stated in alphabetical order. #1 goes to the first-listed substituent. © 2017 Pearson Education, Inc. 14 1/31/18 Two Substituents with the Same Low Number If more than one name has the same low number, choose the name with the next lowest number. © 2017 Pearson Education, Inc. Classification of Alkyl Halides primary alkyl halide = halogen is on a primary carbon secondary alkyl halide = halogen is on a secondary carbon tertiary alkyl halide = halogen is on a tertiary carbon © 2017 Pearson Education, Inc. 15 1/31/18 Common versus Systematic Nomenclature Numbers are used only for systematic names. Common names never have numbers. © 2017 Pearson Education, Inc. Nomenclature of Alkyl Halides © 2017 Pearson Education, Inc. 16 1/31/18 Ethers © 2017 Pearson Education, Inc. Common Names of Ethers The substituents are listed in alphabetical order. © 2017 Pearson Education, Inc. 17 .