C 10 J

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C 10 J

• Synthesis and Reactions of Alkanes

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Nomenclature rules (completion)

• The numerical prefixes di, tri etc are ignored in
  alphabetizing
• The prefixes iso- and cyclo- are considered in
  alphabelizing
• The prefixes tert- and sec- are ignored in
  alphabetizing
• When a noncyclic carbon chain contains more
  carbons than an attached ring, the ring is
  treated as a substituent.

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Examples
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Lecture Outline

• Fundamentals Organic Reaction Mechanisms
• Synthesis of alkanes
• Hydrogenation of alkenes and alkynes
• Reduction with metal/ acid
• Reduction with Lithium aluminium hydride, sodium
  borohydride
• Corey-House Synthesis
• Reaction with Grignard Reagents

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Organic Reaction Mechanisms - Fundamentals

• Categories of organic reactions
• Substitution
• Addition
• Elimination
• Rearrangement

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Fundamentals Organic Reaction Mechanisms

• A reaction mechanism is a step-by-step
  description of the bond-breaking and bond-making
  processes that occur when reagents react to form
  products
• A bond consists of two electrons
• Movement of one electron is denoted by a fishhook
  arrow
• Homolytic cleavage occurs
• Radicals are formed

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• Movement of an electron pair
• (two electrons) is denoted with a curved arrow
  this shows the direction of electron flow in a
  reaction
• heterolytic cleavage

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• Arrows move from a region of high electron
  density to a region of lower electron density
• Electrophile electron-lovers (electron-poor
  reagents/ seeking electrons)
• Nucleophile nucleus lovers (electron-rich
  reagents/ donate electrons to electrophile)

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Resonance

• Resonance arises when two or more structures for
  a molecule can be written with different
  arrangements of the electrons but identical
  arrangements of the atoms

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Synthesis of alkanes

• Catalytic hydrogenation of alkenes/ alkynes
• Syn addition of hydrogen

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The Hydrogenation Reaction

• H2 adsorbs to catalyst surface (Pt, Pd, Ni)
• Syn addition of H2 to double bond

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Reduction with metal and acid
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Reduction with LiAlH4 and NaBH4

• LiAlH4 and NaBH4 function as nucleophiles
• Electrophiles accept electrons to form the bond
• Primary and secondary alkyl halides are reduced
  with NaBH4 while 1o, 2o and 3o alkyl halides are
  reduced with LiAlH4

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Corey-House Synthesis

• Involves the coupling of two alkyl halides to
  form an alkane
• An organolithium compound is formed
• Lithium dialkyl cuprate is formed
• The dialkyl final product is formed

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Corey-House Synthesis

• Preparation of alkyl lithium
• Preparation of lithium dialkyl cuprate

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Corey-House Synthesis

• Preparation of alkane

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Corey-House Synthesis
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(No Transcript)
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Reaction with Grignard reagents

• Grignard reagents are organomagnesium compounds
• Carbon-metal bond

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Grignard

• François Auguste Victor Grignard
• The Nobel Prize in Chemistry 1912

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• Grignard reagents will react with compounds
  containing acidic hydrogen atoms
• Hydrogen atoms attached to electronegative atoms
  (e.g. S, N, O)
• Reaction of Grignard reagent with water

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• Reaction of Grignard reagent with alcohols (H-OR)

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• Reaction of Grignard reagent with 1- alkynes

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• What is the structure of R?

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Exam QuestionDecember 1999

• Suggest structures for alkene A that gives the
  following reaction product. Show all
  possibilities for the structure of A.
• H2(one equiv.), Pd
• (i) A 2-methylhexane

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Lecture Review

• Fundamentals Organic reaction mechanisms
• Synthesis of alkanes
• Hydrogenation of alkenes and alkynes
• Reduction with metal/ acid
• Reduction with Lithium aluminium hydride, sodium
  borohydride
• Corey-House Synthesis
• Reaction with Grignard Reagents
• NEXT LECTURE Reactions of alkanes/ Conformation
  of alkanes Professor H. Jacobs/ Dr. S. Jarrett

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Quotable quotes to remember

• My attitude determines by altitude