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Nomenclature

Nomenclature. Dr. Clower CHEM 2411 Spring 2014 McMurry (8 th ed.) sections 3.2, 3.3, 3.4, 4.1, 4.2, 7.3, 7.4, 9.1, 10.1, 15.1, 17.1,18.1, 18.8, 19.1 , 20.1, 21.1, 24.1, Appendix A. Nomenclature. The naming of organic molecules IUPAC system All names have Substituents- MainChain

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Nomenclature

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  1. Nomenclature Dr. Clower CHEM 2411 Spring 2014 McMurry (8th ed.) sections 3.2, 3.3, 3.4, 4.1, 4.2, 7.3, 7.4, 9.1, 10.1, 15.1, 17.1,18.1, 18.8, 19.1, 20.1, 21.1, 24.1, Appendix A

  2. Nomenclature • The naming of organic molecules • IUPAC system • All names have Substituents-MainChain • Substituents are groups attached to the main chain • MainChain consists of Parent-Infix-Suffix • Parent tells you number of carbons in main chain • Infix tells you if the carbon-carbon bonds are single bonds (saturated molecule) or double or triple bonds (unsaturated molecules) • Suffix tells you the functional group of your molecules

  3. Parent

  4. Straight-chain alkanes

  5. Infix • “-an-” = only carbon-carbon single bonds (saturated) • “-en-” = an alkene (double bond) is present (unsaturated) • “-yn-” = an alkyne (triple bond) is present (unsaturated)

  6. Suffix

  7. Nomenclature • Consider the molecule 2-hexanol. • How many carbons in the main chain? • Saturated or unsaturated? • What functional group? • Consider the molecule octanoic acid. • How many carbons in the main chain? • Saturated or unsaturated? • What functional group? • Consider the molecule 4-methyl-2-pentanamine. • How many carbons in the main chain? • Saturated or unsaturated? • What functional group? • What is 4-methyl?

  8. Substituents • Groups off of main chain (branches) • Parts of larger compounds (not stable by themselves) • Alkyl groups = Alkane – H • “-ane” changes to “-yl” • Methyl • methane – H • CH4 – H • CH3─ • Ethyl • ethane – H • CH3CH3 – H • CH3CH2─

  9. Substituents • Propane – H gives two possible alkyl groups • Propyl • Isopropyl • Similarly, there are multiple alkyl groups with 4 carbon atoms, 5 carbon atoms, etc.

  10. Alkyl groups you need to know • Methyl • Ethyl • Propyl • Isopropyl • Butyl • Isobutyl • sec-butyl • tert-butyl (t-butyl) • Pentyl (amyl) • Isopentyl (isoamyl) • Neopentyl • tert-pentyl • Hexyl, heptyl, etc. • Halogens • Fluoro • Chloro • Bromo • Iodo

  11. Naming alkanes • Find the parent chain • Longest continuous chain of C atoms • Name of chain = parent name • If 2 chains of equal length, parent is the chain with more substituents • Number each carbon in the parent chain • Start from the end closest to the first substituent • If there are substituents equal distance from both ends, number from the end nearest the second substituent

  12. Naming alkanes, cont. • Name and number substituents • Name = alkyl group name • Number = point of attachment to parent chain • Two substituents on the same C get the same number • Write the name as a single word • Substituents before parent name (include #) • Separate # and word with hyphen • Separate two numbers with a comma • List substituents in alphabetical order • Multiple identical substituents use prefixes di, tri, tetra, penta, hexa • DO NOT use sec, tert, di, tri, etc. when alphabetizing • DO use iso, neo when alphabetizing

  13. Examples

  14. Examples • Draw 3-ethylpentane. • Draw all the constitutional isomers with the molecular formula C6H14. Name each isomer.

  15. Examples

  16. Examples

  17. Naming Cycloalkanes • Unsubstituted cycloalkanes: • Add “cyclo” to the parent name • Bicycloalkanes • Two rings • Most common is norbornane • Bicyclo[2.2.1]heptane

  18. Naming Cycloalkanes • Substituted cycloalkanes: • Parent = ring or substituent (whichever has more carbons) • Number the substituents • Do not need to show number if only one substituent on a ring • If two substituents, start with the first alphabetically, number in the direction of the second substituent • If more than two substituents, number so that the substituents have the lowest set of numbers

  19. Examples

  20. Examples

  21. Cycloalkane Stereoisomers • Cycloalkanes are roughly planar • Substituents are either above or below this plane • Shown with dash and wedges • Dash = back; wedge = forward • In a disubstituted cycloalkane, two substituents on the same side (both back or both forward) are cis. Two substituents on opposite sides (one back, one forward) are trans. • Cis and trans versions of the same molecule are stereoisomers

  22. Examples • Do these pairs represent constitutional isomers, cis-trans stereoisomers or the same compound? (a) (b)

  23. Alkene Nomenclature • Similar to alkanes • Change infix from “-an-” to “-en-”

  24. Naming Alkenes • For larger alkenes: • Parent is longest C chain containing both carbons of C=C • Number chain so C=C has lowest possible number • If the double bond is equidistant from both ends, start numbering at end nearest the first substituent • Show location of C=C by first number • Alkenes with >1 C=C use “-adiene”, “-atriene”, etc. in place of “-ene” and show location of all double bonds • Name and number substituents and write the full name • Example:

  25. Examples

  26. Cycloalkenes • The carbon atoms of the C=C are numbered 1 and 2 • Number ring in direction to give first substituent lowest possible number

  27. Alkene substituents

  28. Alkene Stereoisomers • Cis-trans stereoisomers • Seen with disubstituted alkenes • Cis means groups are on the same side of the double bond; trans means groups are on opposite sides • Cannot convert through bond rotation • Example: 2-butene

  29. Examples • Are the following alkenes cis, trans, or neither? (a) (b) (c)

  30. Alkyne Nomenclature • Similar to alkenes • Change infix from “-en-” to “-yn-”

  31. Naming Alkynes • For larger alkynes: • Parent is longest C chain containing both carbons of C≡C • Number chain so C≡C has lowest possible number • If the triple bond is equidistant from both ends, start numbering at end nearest the first substituent • Show location of C≡C by first number • Alkynes with >1 C≡C use “-adiyne”, “-atriyne”, etc. in place of “-yne” and show location of all double bonds • Name and number substituents and write the full name • Example:

  32. Enyne • Contains both alkene and alkyne • Number from end closest to first multiple bond (either C=C or C≡C) and show both numbers • If the C=C and C≡C are equidistant from the ends, C=C gets the lower number • Examples:

  33. Naming Aromatic Compounds • Benzene • Monosubstituted benzenes • Substituent name + “benzene”

  34. Common Benzene Compounds

  35. Benzene Nomenclature • If substituent has greater than 6 carbons, it becomes the parent, and benzene is called a phenyl group • Benzene substituents:

  36. Disubstituted Benzenes • ortho (1,2) • meta (1,3) • para (1,4)

  37. Naming Disubstituted Benzenes • If one substituent is part of a common name, that name is the parent and that substituent is at carbon 1 • If neither substituent is part of a common name, list the substituents in alphabetical order (first alphabetically is at carbon 1) • If both substituents are part of common name, use this order of priority to determine the parent name: -CO2H > -CHO > -OH > -NH2 > -CH3

  38. Examples

  39. Examples

  40. Naming Polysubstituted Benzenes • With 3 or more substituents do not use ortho, meta, para • Number ring to give smallest set of numbers • If a common name, use as parent (substituent at carbon 1) • List substituents in alphabetical order

  41. Examples

  42. Another Aromatic Compound • Pyridine • If substituted, nitrogen is atom 1 of the ring. Number in direction of other substituents.

  43. Naming Alcohols • Acyclic alcohols • Parent chain is longest chain containing C bonded to –OH • Change suffix from “-e” to “-ol” • Number from end closest to –OH. Show location of –OH. • Name/number substituents • Cyclic alcohols • Ring is the parent • Number ring so –OH is at carbon 1 and other substituents have lowest possible numbers. You do not need to show the location of the –OH. • Name/number substituents.

  44. Naming Alcohols • Multiple hydroxyl groups • Two –OH groups is a diol; 3 is a triol • Two adjacent –OH groups is a glycol • Name as acyclic alcohols, except keep the “-e” suffix and add “-diol” • Indicate numbers for all –OH groups • Unsaturated alcohols (enol or ynol) • Parent chain contains carbon bonded to –OH and both carbons of C=C or C≡C • Suffix is “-ol”, infix is “-en-” or “-yn-” • Number chain so –OH has the lowest number • Show numbers for –OH and the unsaturation • Name/number substituents

  45. Examples

  46. Examples

  47. Naming Thiols • Thiols are sulfur analogs of alcohols • Name like alcohols, but keep the “-e” and use “-thiol” in place of “-ol”

  48. Naming Amines • Parent chain is longest containing C bonded to –N • Change suffix “-e” to “-amine” • Number from end closest to –N. Show location of –N. • Name/number substituents

  49. Examples

  50. Naming Aldehydes • Parent chain contains carbon of CHO • Suffix is “-al” • CHO carbon is carbon 1 (do not need to show in name)

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