An Introduction to Organic Compounds: Chapter 3

1. An Introduction to Organic Compounds:Chapter 3 Nomenclature, Physical Properties, and Representation of Structure Chapter 3

2. Contents of Chapter 2 • Nomenclature • Structures of Alkyl Halides, Alcohols, Ethers, and Amines • Physical Properties • Conformations of Alkanes • Cycloalkanes Chapter 3

3. Counting to Ten in Organic • 01 = meth Mother • 02 = eth Enjoys • 03 = prop Peanut • 04 = but BUTter • 05 = pent PENTagon • 06 = hex HEXagon or HEX nut • 07 = hept HEPTember (Roman sept is Greek hept) • 08 = oct OCTober • 09 = non NONember (Roman nov is Greek non) • 10 = dec DECember Chapter 3

4. Alkanes Chapter 3

5. Primary, Secondary, Tertiary • A primary carbon has one other C directly bonded to it. • A secondary carbon is directly bonded to two other C’s. • A tertiary carbon is directly bonded to three other C’s. • Multivalent atoms are 1º, 2º, or 3º by bonding to C’s. • Univalent atom or group not really 1º, 2º, or 3º on its own - ID depends on type of carbon it is bonded to. Chapter 3

6. Nomenclature of Alkyl Substituents • There are four alkyl groups that contain four carbons Chapter 3

7. Nomenclature of Alkyl Substituents • The prefix sec- occurs only in sec-butyl Chapter 3

8. Nomenclature of Alkyl Substituents • The prefix tert- can be used withbutyl or pentyl (also known as amyl) but not with hexyl Chapter 3

9. IUPAC Systematic Nomenclature - Alkanes • Determine longest continuous chain (i.e. parent hydrocarbon) • Cite the name of substituent before the name of the parent hydrocarbon along with the number of the carbon to which it is attached Chapter 3

10. IUPAC Systematic Nomenclature - Alkanes • Number in the direction that gives the lower number for the lowest-numbered substituent. Substituents are listed in alphabetical order – neglecting prefixes such as di- tri- tert- etc. Chapter 3

11. IUPAC Systematic Nomenclature - Alkanes • When both directions yield the same lower number for the lowest numbered substituent, select the direction that yields the lower number for the next lowest numbered substituent Chapter 3

12. IUPAC Systematic Nomenclature - Alkanes • If same substituent numbers are obtained in either direction, number in direction giving lowest number to the first named substituent Chapter 3

13. IUPAC Systematic Nomenclature - Alkanes • If compound has two or more chains of the same length, parent hydrocarbon is chain with greatest number of substituents Chapter 3

14. IUPAC Systematic Nomenclature - Alkanes • Names such as sec-butyl and tert-butyl are acceptable, but systematic substituent names are preferable • Numbering of the substituent begins with the carbon attached to the parent hydrocarbon • This number together with the substituent name is placed inside parentheses Chapter 3

15. Nomenclature of Cycloalkanes • Cycloalkanes generally are shown as skeletal structures Chapter 3

16. Nomenclature of Cycloalkanes • Ring is the parent hydrocarbon unless the alkyl substituent has more carbons; in that case the substituent becomes the parent hydrocarbon • If only one substituent, no need to give it a number Chapter 3

17. Nomenclature of Cycloalkanes • If the ring has 2 substituents, list in alphabetical order and give number 1 to first named group Chapter 3

18. Nomenclature of Cycloalkanes • If there is more than one substituent, list in alphabetical order; one substituent is given the position number 1; number either clockwise or counterclockwise - lowest numbers Chapter 3

19. Nomenclature of Alkyl Halides • Common name - Name the alkyl group first, followed by the name of the halogen expressed as an -ide name Chapter 3

20. Nomenclature of Alkyl Halides • IUPAC name - The halogen is treated as a substituent Chapter 3

21. Nomenclature of Ethers • Common name - Name(s) of alkyl group(s) listed first followed by the word “ether” Chapter 3

22. Nomenclature of Ethers • IUPAC name - The smaller alkyl group is converted to an “alkoxy” name and used as a substituent Chapter 3

23. Nomenclature of Alcohols • Common name - Name of the Alkyl group followed by the word “alcohol” Chapter 3

24. Nomenclature of Alcohols • IUPAC name - The OH group is a site of reactivity (a functional group) • Functional group is denoted by the suffix, “ol” methanol ethanol Chapter 3

25. IUPAC Nomenclature of Alcohols • Parent Hydrocarbon is the longest continuous chain that contains the OH • Number the chain in direction that gives functional group the lowest number • If both a substituent and a functional group are present, the functional group gets the lower number Chapter 3

26. IUPAC Nomenclature of Alcohols • If the functional group gets the same number when counted from both directions, use direction which gives the substituent the lower number • If there is more than one substituent, cite substituents in alphabetical order Chapter 3

27. IUPAC Nomenclature of Alcohols • System is summarized as [Substituent] [Parent Hydrocarbon] [Functional Group] Chapter 3

28. Nomenclature of Amines • Common name - Name of the Alkyl group(s) (in alphabetical order) followed by the syllable “amine” • The whole name is a single word methylamine methylpropylamine Chapter 3

29. Nomenclature of Amines • IUPAC name - The NH2 group is a site of reactivity (a functional group) • Functional group is denoted by the suffix, “amine” • Final “e” of longest alkane group replaced by suffix “amine” (don’t run vowels together) 1-butanamine butan-1-amine Chapter 3

30. IUPAC Nomenclature of Amines • Find the longest chain bonded to the nitrogen • Final “e” is replaced with “amine” • Number the carbon to which nitrogen is bonded • Number any substituents on the alkyl chain • Use italicized N- for each additional substituent(s) on the nitrogen Chapter 3

31. Properties of Alkyl Halides, Alcohols, Ethers, & Amines • For alkanes, there are only induced dipole-induced dipole interactions (also known as van der Waals forces or London forces) • van der Waals forces are a function of surface area Chapter 3

32. Induced Dipole-Induced Dipole Interactions Chapter 3

33. Hydrogen Bonding: Strong Dipole-Dipole Interactions Chapter 3

34. Dipole-dipole Interactions • Particularly important for alcohols and amines • Ethers and alkyl halides have dipole moments, but their intermolecular attractions are not as strong as hydrogen bonds Chapter 3

35. Comparative Boiling Points Chapter 3

36. Solubility • The more carbons that are present, the less soluble an organic compound is in water Chapter 3

37. Conformations of Alkanes: Rotation About C-C Single Bonds Chapter 3

38. Drawing Cyclohexane in the Chair Conformation Chapter 3

39. Interconversion of Cyclohexane Conformations • As a result of simultaneous rotation about all C-C bonds, a chair conformation of cyclohexane can interconvert to another chair conformation by a ring-flip • In the process, equatorial bonds become axial and vice versa Chapter 3

40. Monosubstituted Cyclohexanes • When there is one substituent on the cyclohexane ring, the two chair conformations are no longer equivalent Chapter 3

41. Conformations of 1,4-Disubstituted Cyclohexanes two methyl groups on opposite sides of ring two methyl groups on same side of ring cis-1,4-dimethylcyclohexane trans-1,4-dimethylcyclohexane Chapter 3

42. Conformations of 1,4-Disubstituted Cyclohexanes • The cis isomer must have one substituent in an axial position and one in an equatorial position ring-flip equatorial axial axial cis-1,4-dimethylcyclohexane Chapter 3

43. Conformations of 1,4-Disubstituted Cyclohexanes • The trans isomer has both substituents in either the equatorial or in the axial positions axial ring-flip equatorial equatorial axial much more stable much less stable trans-1,4-dimethylcyclohexane Chapter 3

44. Conformations of cis-1,3-Disubstituted Cyclohexanes • A cis-1,3-disubstituted cyclohexane can exist in one of two conformations ring-flip much more stable much less stable cis-1-tert-butyl-3-methylcyclohexane Chapter 3

45. Conformations of trans-1,3-Disubstituted Cyclohexanes • Both conformers of trans-1-tert-butyl-3-methylcyclohexane have one substituent in an axial position and one in an equatorial position Chapter 3