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Organic Halides

Organic Halides. Functional Group. A structural unit in a molecule responsible for its characteristic behavior under a particular set of reaction conditions. Families of organic compounds and their functional groups. Alcohol ROH Alkyl halide R X ( X = F, Cl, Br, I)

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Organic Halides

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  1. Organic Halides

  2. Functional Group • A structural unit in a molecule responsible for itscharacteristic behavior under a particular set ofreaction conditions

  3. Families of organic compoundsand their functional groups • Alcohol ROH • Alkyl halide RX (X = F, Cl, Br, I) • Amine primary amine: RNH2 • secondary amine: R2NH • tertiary amine: R3N

  4. IUPAC Nomenclatureof Alkyl Halides

  5. IUPAC Nomenclature There are several kinds of IUPAC nomenclature. • The two that are most widely used are:functional class nomenclaturesubstitutive nomenclature • Both types can be applied to alcohols andalkyl halides.

  6. CH3CH2CHCH2CH2CH3 H I Br Functional Class Nomenclature of Alkyl Halides • Name the alkyl group and the halogen asseparate words (alkyl + halide) CH3CH2CH2CH2CH2Cl CH3F

  7. CH3CH2CHCH2CH2CH3 H I Br Functional Class Nomenclature of Alkyl Halides • Name the alkyl group and the halogen asseparate words (alkyl + halide) CH3F CH3CH2CH2CH2CH2Cl Methyl fluoride Pentyl chloride 1-Ethylbutyl bromide Cyclohexyl iodide

  8. CH3CHCH2CH2CH3 Br CH3CH2CHCH2CH3 I Substitutive Nomenclature of Alkyl Halides • Name as halo-substituted alkanes. • Number the longest chain containing thehalogen in the direction that gives the lowestnumber to the substituted carbon. CH3CH2CH2CH2CH2F

  9. CH3CHCH2CH2CH3 Br CH3CH2CHCH2CH3 I Substitutive Nomenclature of Alkyl Halides • Name as halo-substituted alkanes. • Number the longest chain containing thehalogen in the direction that gives the lowestnumber to the substituted carbon. CH3CH2CH2CH2CH2F 1-Fluoropentane 2-Bromopentane 3-Iodopentane

  10. Cl CH3 CH3 Cl Substitutive Nomenclature of Alkyl Halides • Halogen and alkyl groupsare of equal rank when it comes to numberingthe chain. • Number the chain in thedirection that gives the lowest number to thegroup (halogen or alkyl)that appears first.

  11. Cl CH3 CH3 Cl Substitutive Nomenclature of Alkyl Halides 5-Chloro-2-methylheptane 2-Chloro-5-methylheptane

  12. Nomenclature of Alkyl Halides In the IUPAC system, alkyl halides are named as substituted alkanes

  13. CH3 CH3CHCH2CH2CH3 CH3CCH2CH2CH3 Br OH Classification H CH3CH2CH2CH2CH2F OH primary alkyl halide secondary alcohol secondary alkyl halide tertiary alcohol

  14. Different Kinds of Alkyl Halides

  15. Aryl Halides • Aryl halides are halides in which the halogen is attached directly to an aromatic ring. • Carbon-halogen bonds in aryl halides are shorter and stronger than carbon-halogen bonds in alkyl halides.

  16. Aryl Halides • Aryl halides are halides in which the halogen is attached directly to an aromatic ring. • Carbon-halogen bonds in aryl halides are shorter and stronger than carbon-halogen bonds in alkyl halides. • Because the carbon-halogen bond is stronger, aryl halides react more slowly than alkyl halides when carbon-halogen bond breaking is rate determining.

  17. Boiling point increases with increasingnumber of halogens Compound Boiling Point • CH3Cl -24°C • CH2Cl2 40°C • CHCl3 61°C • CCl4 77°C Even though CCl4 is the only compound in this list without a dipole moment, it has the highest boiling point. Induced dipole-induced dipole forces are greatest in CCl4 because it has the greatest number of Cl atoms. Cl is more polarizable than H.

  18. Cl Cl Physical Properties of Aryl Halides • resemble alkyl halides • all are essentially insoluble in water • less polar than alkyl halides  2.2 D  1.7 D

  19. least reactive most reactive Reaction of Alcohols with Hydrogen Halides ROH + HX RX + HOH • Hydrogen halide reactivity HF HCl HBr HI

  20. An SN2 reaction proceeds in the direction that allows the strongest base to displace the weaker base

  21. 1. NaOH, H2O 370°C Cl OH 2. H+ Example (97%)

  22. Cl OCH3 NO2 NO2 But... • nitro-substituted aryl halides do undergonucleophilic aromatic substitution readily CH3OH + + NaOCH3 NaCl 85°C (92%)

  23. F OCH3 NO2 NO2 Reaction CH3OH + + NaOCH3 NaF 85°C (93%)

  24. Cl NH2 Aryl Halides Undergo Substitution WhenTreated With Very Strong Bases KNH2, NH3 –33°C (52%)

  25. * Cl OH * OH * Hydrolysis of Chlorobenzene • 14C labeling indicates that the high-temperature reaction of chlorobenzene with NaOH goes via benzyne. NaOH, H2O 395°C + (43%) (54%)

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