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Chapter 4

Chapter 4. Nomenclature. Nomenclature of Alcohol. Nomenclature of Alcohol. Determine the longest chain of carbon to which the hydroxyl is directly attached and name it Drop the final -e to suffix –ol E.g methan e  methan ol

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Chapter 4

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  1. Chapter 4 Nomenclature

  2. Nomenclature of Alcohol

  3. Nomenclature of Alcohol • Determine the longest chain of carbon to which the hydroxyl is directly attached and name it • Drop the final -e to suffix –ol • E.g methane methanol • Number the longest chain so that the carbon atom bearing the hydroxyl group will have the lowest number.

  4. Nomenclature of Alcohol

  5. Common functional names of alcohol

  6. Example • Draw bond-line formulas and give IUPAC substituted names for all of the isomeric alcohol with the formula C4H10O

  7. 4.4 Monocyclic Compound • Cycloalkanes with only one ring are name by attaching the prefix “cyclo-” to the name of the alkanes

  8. Cyclic alkanes • If a cyclic alkane and one substituent is present, no need to designated position of substituent

  9. Cyclic alkanes • If a cyclic alkane and two substituents are presented, we number the ring beginning with the substituent first in the alphabet and number in the direction that gives the next substituent the lower number possible

  10. Cyclic alkanes • If a cyclic alkane and three or more substituents are presented, we begin at the substituent that leads to the lowest set of locants

  11. Cyclic alkanes • When a single ring system is attached to a single chain with a greater number of carbon atoms, or when more than one ring system is attached to a single chain, then

  12. 4.4 Bicyclic compounds • A compound is considered bicyclic is when it contains two fused or a bridged ring • The name of bicyclicalkane is corresponding to the total number of carbon presented.

  13. Bicyclic alkanes • If substituents are present, we number the bridge ring system beginning at on bridge-head, proceeding first along the longest bridge to the other bridge-head. The shortest bridge is named last

  14. 4.5 Nomenclature of Alkenes and Cycloalkenes • Rules for naming alkenes • Identify and name the longest chain of carbon atoms that contain C=C • Parent name contains suffix -ene • Number the carbon chain from one to the other, so as to give the lowest number to a double bond • Designated the location of the double bond to the parent name • Identify substituents and their locations

  15. 4.5 Nomenclature of Alkenes and Cycloalkenes • Rules for naming cycloalkenes • Identify and name the longest chain of carbon atoms that contain C=C • Parent name contains suffix -ene • Number the carbon chain from one to the other, starting with the double bond • Identify substituents and their locations

  16. 4.5 Nomenclature of Alkenes and Cycloalkenes • Name compounds containing a double bond and an alcohol as alkenol (cycloalkenol) • Give the alcohol carbon the lower number

  17. 4.5 Nomenclature of Alkenes and Cycloalkenes • Two common alkenyl groups

  18. 4.5 Nomenclature of Alkenes and Cycloalkenes

  19. 4.5 Nomenclature of Alkenes and Cycloalkenes • If two identical substituents are on the same side of the double bond, the compound is designated cis • If they are opposite, the compound is designated trans

  20. Nomenclature of Alkynes • Rules for naming an alkynes are similar to alkene BUT • Parent name ends with -yne

  21. Example • Name the following compound • Draw the geometric isomers of 2-butene. Label them cis and trans

  22. Nomenclature of Alkynes • Monosubstituted acetylene or 1-alkyne are called terminal alkynes

  23. 4.7 Physical Properties Alkanes and Cycloalkanes Boiling point: increases with increasing molecular weight - unbranched molecules (homologous series) Branched alkanes have lowers boiling point - affected by van der Waals forces

  24. 4.7 Physical Properties Alkanes and Cycloalkanes Melting Points: - increasing but does not show the same smooth curve - alternation from odd and even number of carbon atoms - alkane chains with an even number of carbon atom pack more closely in the crystalline state  higher mp  cycloalkanes also have higher m.p

  25. 4.7 Physical Properties Alkanes and Cycloalkanes • Density: Alkanes and cycloalkanes are the least dense of all group in organic compound. • E.g < 1.00 g/ml at 4oC • Solubility: alkanes and cycloalkanes are almost insoluble in water • Due to their low polarity and inability to form H-bond • “like dissolves like”

  26. 4.7 Physical Properties Alkanes and Cycloalkanes • Recall

  27. 4.7 Physical Properties Alkanes and Cycloalkanes • Only sigma (σ) bond can undergo rotation about that bond with respect to each other • Each possible structure that result from rotation of group about the signma bond is called confomormational isomers • Types: Newman projection formula and sawhorse formula

  28. Conformational isomers

  29. Conformational isomers Eclipsed conformation Staggered conformation • Each hydrogen on one carbon as close as possible to one hydrogen on the other carbon • Hydrogen on one carbon as far from the hydrogen from other carbon

  30. Potential energy diagram

  31. Conformational isomers • G is a group or atom other than hydrogen Barriers to rotation are somewhat larger

  32. 4.9Conformational Analysis of Butane

  33. Example • Using Newman projections to draw out all possible conformations of 1,2-dibromomethane

  34. Example • Draw a plot of energy versus dihedral angle for the conformation of 2-methylbutane about the C2-C3 bond

  35. Stereoisomers and Conformational Stereoisomers • Stereoisomers have the same molecular formula and connectivity but different arrangements of atoms in 3-D • Conformational Stereoisomers: Stereoisomers that are interconvertible with one another by bond rotation

  36. The Relative Stabilities of Cycloalkanes: Ring Strain • Carbon chains are confined in rings, cycloalkanes are much less flexible than monocyclic alkanes. • Strain energy is measure from the amount of heat that is produced from combustion reaction • Ring strain describe the destabilization of a cyclic molecule

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