《有机化学》课程PPT教学课件（Organic Chemistry with Biological Applications, 3th Edition, John McMurry, 2016）Chapter 04 Organic Compounds - Cycloalkanes and Their Stereochemistry

CNGNGE JOHN MCMURRY CHAPTER 4 Organic Compounds: Cycloalkanes and Their Stereochemistry IH1 RD EDIION Organic Chemistry with Biological Applications

CHAPTER 4 Organic Compounds: Cycloalkanes and Their Stereochemistry

Cyclics Most organic compounds contain rings of carbon atoms Chrysanthemic acid H3C CH3 Occurs naturally as esters -Active insecticidal Chrysanthemic acid -H constituents of chrysanthemum CO>H flowers Prostaglandins CO2H Potent hormones Prostaglandin E1 CH3 Control physiological functions HO in humans HO CH2OH Steroids CH3 0 Contain four joined rings OH Naturally occurring hormones CH3 Cortisone in plants and animals H

Most organic compounds contain rings of carbon atoms Cyclics Chrysanthemic acid ▪ Occurs naturally as esters ▪ Active insecticidal constituents of chrysanthemum flowers Prostaglandins ▪ Potent hormones ▪ Control physiological functions in humans Steroids ▪ Contain four joined rings ▪ Naturally occurring hormones in plants and animals

4-1 Naming Cycloalkanes Cycloalkanes or Alicyclic Compounds_(aliphatic cyclic) Saturated cyclic hydrocarbons containing rings of carbon atoms (CH2)n or CnH2n Cyclopropane Cyclobutane Cyclopentane Cyclohexane Cengago Leaming.All Rights Rasorvod

Cycloalkanes or Alicyclic Compounds (aliphatic cyclic) ▪ Saturated cyclic hydrocarbons containing rings of carbon atoms ▪ (CH2 )n or CnH2n 4-1 Naming Cycloalkanes

Naming Cycloalkanes Step 1-Find the parent by counting carbon atoms Named as alkyl-substituted cycloalkane The number of carbon atoms in the ring is equal to or greater than the number in the substituent Named as cycloalkyl-substituted alkane The number of carbon atoms in the largest substituent is greater than the number in the ring CH3 CH2CH2CH2CH3 3 carbons 4 carbons Methylcyclopentane 1-Cyclopropylbutane

Named as alkyl-substituted cycloalkane ▪ The number of carbon atoms in the ring is equal to or greater than the number in the substituent Named as cycloalkyl-substituted alkane ▪ The number of carbon atoms in the largest substituent is greater than the number in the ring Step 1 – Find the parent by counting carbon atoms Naming Cycloalkanes

Naming Cycloalkanes Step 2-Number the substituents,and write the name Choose attachment point as carbon 1 and number carbon atoms on the ring so that second substitutent has lowest number possible. CH3 CH3 6 2 6 3 NOT 5 5 3 4 CH3 CH3 1,3-Dimethylcyclohexane 1,5-Dimethylcyclohexane Lower Higher Cengg Leaming All Pits Paserved

▪ Choose attachment point as carbon 1 and number carbon atoms on the ring so that second substitutent has lowest number possible. Step 2 – Number the substituents, and write the name Naming Cycloalkanes

Naming Cycloalkanes If ambiguity exists,number H3C、6 1CH2CH3 carbon atoms so that third or fourth substituent has lowest -CH3 number possible. 3 1-Ethyl-2,6-dimethylcycloheptane H3C、4 2CH2CH3 Higher NOT CH3 6 H3C. CH2CH3 2-Ethyl-1,4-dimethylcycloheptane CH3 Lower Lower 6 5 3-Ethyl-1,4-dimethylcycloheptane Higher LmingAl Pigh Reerd

Naming Cycloalkanes ▪ If ambiguity exists, number carbon atoms so that third or fourth substituent has lowest number possible

Naming Cycloalkanes When two or more substituents could potentially receive the same numbers,number by alphabetical priority: CH3 CH3 1 CH2CH3 CH2CH3 3 5 2 NOT 3 1-Ethyl-2-methylcyclopentane 2-Ethyl-1-methylcyclopentane

▪ When two or more substituents could potentially receive the same numbers, number by alphabetical priority: Naming Cycloalkanes

Naming Cycloalkanes If halogens are present,treat them just like alkyl groups: CH3 CH3 2 NOT Br Br 1-Bromo-2-methylcyclobutane 2-Bromo-1-methylcyclobutane Additional examples: C B CH3 CH3 6 CHCH2CH3 5 CH3CH2 CH3 CH2CH3 1-Bromo-3-ethyl-5-methyl- (1-Methylpropyl)cyclobutane 1-Chloro-3-ethyl-2-methyl- cyclohexane or sec-butylcyclobutane cyclopentane Cangge Leaming All Pighs Resorved

▪ If halogens are present, treat them just like alkyl groups: ▪ Additional examples: Naming Cycloalkanes

4-2 Cis-Trans Isomerism in Cycloalkanes Cycloalkanes vs.Open-chain Alkanes Similarities -nonpolar;fairly inert Differences-cycloalkanes are less flexible than open- chain alkanes Rotation occurs around the carbon-carbon bond in ethane No rotation is possible around the carbon-carbon bonds in cyclopropane without breaking open the ring Larger cycloalkanes have increasing rotational freedom (a) Rotate

Cycloalkanes vs. Open-chain Alkanes ▪ Similarities – nonpolar; fairly inert ▪ Differences – cycloalkanes are less flexible than open￾chain alkanes ▪ Rotation occurs around the carbon-carbon bond in ethane ▪ No rotation is possible around the carbon-carbon bonds in cyclopropane without breaking open the ring ▪ Larger cycloalkanes have increasing rotational freedom 4-2 Cis-Trans Isomerism in Cycloalkanes

Cis-Trans Isomerism in Cycloalkanes Cycloalkanes:Two faces (as viewed edge on) Top face Bottom face Isomerism possible in substituted cycloalkanes cis-1,2-Dimethylcyclopropane trans-1,2-Dimethylcyclopropane

▪ Cycloalkanes: Two faces (as viewed edge on) Top face Bottom face ▪ Isomerism possible in substituted cycloalkanes Cis-Trans Isomerism in Cycloalkanes