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CHEM 109A Organic Chemistry

Chapter 3 An Introduction to Organic Compounds

Nomenclature, Physical Properties, and Structure

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HO

How many hydrogens are attached to each carbon

cholesterol

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Alkanes are Saturated Hydrocarbons, CnH2n+2, Only Single Bonds

heating power

bbq lighters

gasoline

jet fuel

diesel

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Types of Alkanes in Chapter 3

straight chain (CnH2n+2)

branched (CnH2n+2)

cyclic (CnH2n)

cyclohexane hexane

butane

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Alkanes and Alkyl Groups: Two alkanes C4H10

CH3CH2CH2CH3

Butane

CH3CH2CH2CH2−X

Butyl group

and Isobutane

CH3CH(CH3)2

Isobutane

(CH3)3C−X

tert-butyl group

Butane

and

CH3CH2CHCH2

sec-butyl group

X

X

X

CH3 CHCH3

CH3

XX

and

(CH3)2CHCH2−X

isobutyl group

butane and isobutane are constitutional isomers

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Alkyl Substituents

X

ethyl group

X

X X

n-propyl group n-butyl group n-pentyl group

R X

generic alkyl group

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n = an Unbranched Chain

Commonnamessometimesuse“n”(standsfor“normal”)toindicateastraight-chainalkane.

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Alkyl Substituents

X

ethyl group

X

X X

n-propyl group n-butyl group n-pentyl group

R X

generic alkyl groupsec-butyl group

X X

isobutyl group

branched alkyl groups

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Primary, Secondary, and Tertiary Carbons

•  Aprimarycarbonisbondedtoonecarbon.

•  Asecondarycarbonisbondedtotwocarbons.•  Atertiarycarbonisbondedtothreecarbons.

• Primaryhydrogensareattachedtoprimarycarbons.

• Secondaryhydrogensareattachedtosecondarycarbons.

• Tertiaryhydrogensareattachedtotertiarycarbons.

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Common Types of Organic Compounds

ROR X R OH R NH2

X = F, or Cl, or Br, or I

an alkyl halide an alcohol an ether an alkyl amine

RR

HN

R

RN

R

R

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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)

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sec-Pentyl is Not a Good Name

Anamemustspecifyonlyonecompound.

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“tert” Can Be Used with “Butyl” and “Pentyl”

tert-hexylisnotagoodname.

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“Iso”

Isoisatoneend,andthegroupreplacingtheHisattheotherend.

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Alkyl Group Names

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Nomenclature of Alkanes

Firstidentifythelongestcontinuouschain

(theparenthydrocarbon)

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Add the Name of the Substituent

Numberthechaininthedirectionthatgivesthesubstituentaslowanumberaspossible.

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Common versus Systematic Nomenclature

Commonnamesneverhavenumbers.Onlysystematicnameshavenumbers.

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List Substituents in Alphabetical Order

Thecorrectnameistheonethatcontainsthelowestnumber.

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Multiple Substituents

Thechainisnumberedinthedirectionthatputsthelowestnumberinthename.

Substituentsarelistedinalphabeticalorder.(di,tri,tetra,sec,tertarenotalphabetized)

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When Both Have the Same Lowest Number

Whenbothnameshavethesamelowestnumber,goforthenextlowestnumber.

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When Both Have the Same Numbers

Whenthesamenumbersareobtainedinbothdirections,thefirstgrouplistedgetsthelowernumber.

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Branched Substituents

Ifthesubstituenthasacommonname,thecommonnamecanbeusedinsteadoftheparentheticalname.

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Branched Substituents

Ifthesubstituentdoesnothaveacommonname,theparentheticalnamehastobeused.

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Chains with the Same Length

Whentwoormorechainshavethesamelength,theparenthydrocarbonisthechainwiththemostsubstituents.

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Cycloalkanes

SkeletalstructuresdonotshowCsandHsbondedtoCs.

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Monosubstituted Cycloalkanes

Anumberisnotneeded.

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Disubstituted Cycloalkanes

Substituentsarestatedinalphabeticalorder.#1goestothefirst-listedsubstituent.

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Two Substituents with the Same Low Number

Ifmorethanonenamehasthesamelownumber,choosethenamewiththenextlowestnumber.

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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

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Common versus Systematic Nomenclature

Numbersareusedonlyforsystematicnames.Commonnamesneverhavenumbers.

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Nomenclature of Alkyl Halides

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Ethers

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Common Names of Ethers

Thesubstituentsarelistedinalphabeticalorder.