Organische Chemie 1A

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Organische Chemie 1A Prof. dr. Floris Rutjes
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Organische Chemie 1A
Docent Prof. dr. Floris Rutjes UL 354, tel.
53202, rutjes_at_sci.kun.nl Werkcollege
assistenten Pieter de Witte Bas Gruijters Boek
Maitland Jones, Jr., Organic Chemistry, 2nd
Ed. Aanbevolen Student Version (antwoorden op
vragen uit het boek)
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Organische Chemie 1A

• Hoor- en werkcolleges worden door elkaar heen
  gegeven
• Per week vijf college-uren en een tutoruur
• Tutoruur heeft andere opzet met open vragen
• College wordt gegeven met PP slides
• PP files worden uitgereikt als dictaat
• Zijn ook na te lezen op de website
  http//www.kun.etc
• Belangrijke aankondigingen betreffende dit
  college zijn hier ook te vinden.

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What is organic chemistry ?

• Virtually anything around you.....
• Raincoat (polymers)
• Duo Penotti (food chemistry)
• After shave (flavor and fragrance industry)
• Paracetamol (against your hangover)
• Medicines (pharmaceutical industry)
• EPO, anabolic steroids
• Etcetera, etcetera.......

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History of Organic Chemistry

• 1828 synthesis of urea (Wöhler)
• 1995 synthesis of brevetoxin B (Nicolaou)

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Recent Nobel Prizes (1990)
From the Boston Globe, on October 18, 1990
Harvard professor E. J. Corey earned the Nobel
Prize for chemistry in 1990 for his work
simplifying the formulation of complex
pharmaceuticals. Elias James Corey was a whiz
kid from Methuen who wrote his doctoral thesis in
four weeks, earned a PhD at age 22 and was made a
full professor at 27. Yesterday, at 62, he won an
award that friends and colleagues said was years,
even decades, overdue the Nobel Prize in
Chemistry. His hobbies? Prof. David A. Evans, a
fellow chemistry professor at Harvard, put it
bluntly, "Chemistry. He works seven days a week."
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Recent Nobel Prizes (1996)
Buckminsterfullerene, C60
http//www.ch.ic.ac.uk/motm/c60.html

• The serendipitous discovery of a new form of
  carbon in 1985 uncovered a fundamentally
  different structure of closed carbon cages, which
  were to become known as fullerenes.
• 1996 Nobel Prize for chemistry to Curl, Jr.,
  Kroto and Smalley.

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Het belang van natuurstoffen
The tropical frog Epipedobates tricolor is the
original source of the chemical epibatidine. It
has no natural enemies because a single tiny frog
contains within its skin enough frightful
chemistry to rub out a water buffalo!
Inspired by the intriguing properties of
epibatidine, Abbot researchers started to
synthesize analogues with potentially less side
effects. One of them was ABT-594. It proved to be
as effective as morphine, significantly less
toxic than epibatidine and, in addition, appeared
to be non-addictive. This is because it does not
act through the opioid receptors.
http//www.abdn.ac.uk/chemistry/abt/
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Another example desogestrel

• Active component in oral contraceptives (Organon)
• Synthesized in a 20 step procedure on ton scale
  (Diosynth)

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Doel van college OC1A/1B

• Begrijpen van de structuur op atomair en
  moleculair niveau
• Verklaren van eigenschappen van moleculen op
  basis van hun elektronische structuur
• Verklaren en opstellen van reactiemechanismen
• Voorspellen van de reactiviteit van functionele
  groepen
• Kennismaken met een aantal basisreacties

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Atoms and Atomic Orbitals

• The Basis is the Periodic Table of the Elements

http//hera.roca.csic.es/periodic/periodic-main.ht
ml
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The octet rule

• Atoms prefer to have completely filled shells
  so-called noble gas configuration
• Na prefers to be Na, Cl prefers to be Cl_
• Elements of the second row can host 8 electrons

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Lewis structures

• Lewis structures are structural formulas showing
  all valence electrons
• Count the total of valence electrons, divide
  them over the molecule following the octer rule

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Electronegativity chart
H 2.3
He
Be 1.6
Li 0.9
B 2.1
C 2.5
N 3.1
O 3.6
F 4.2
Ne
Na 0.9
Mg 1.3
Al 1.6
Si 1.9
P 2.3
S 2.6
Cl 2.9
Ar
K 0.7
Br 2.7
Rb 0.7
I 2.4

• The electronegativity increases from left to
  right and from bottom to top in the periodic
  table

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Formal charge

• The amount of valence electrons present
  determines the formal charge of the atom

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Stabilization by delocalization

• Both structures are mesomeric or resonance
  structures
• All s-bonds remain in tact
• Shift p- and free electron pairs, but obey the
  octet rule

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Structure vs Reactivity

• Mesomeric structures can be invoked to explain
  the reactivity of functional groups

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Alkanes
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The structure of methane

• The 2s and the 3 2p orbitals of carbon are
  mathematically combined to form four equivalent
  sp3-hybridized orbitals

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The CH-bond in methane

• Overlap with the 1s orbitals of hydrogen
  generates a stable CH-bond a so-called s-bond
• Dissociation energy ca. 104 kcal/mol

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sp2-hybridization

• 2s 2px 2py gives three sp2 hybridized
  orbitals
• Orbitals are in the same plane with angles of 120
  degrees

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sp-hybridization

• Combination of the 2s and the 2p orbital leads to
  2 sp hybrid orbitals
• Both are in a linear orientation (bond angle 180
  degrees)

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Homolytic vs Heterolytic Bond cleavage

• For homolytic cleavage of the H-H bond, the
  required energy is 104 kcal/mol. This is called
  the bond dissociation energy
• Note the different arrows !

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Ionic forms of carbon (2.4)

• What is the 3-dimensional structure of
  carbocations and carbanions ?

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The carbocation

• A carbocation is sp2-hybridized, with angles of
  120 degrees between the substituents
• Orthogonal to the plane, there is an empty
  p-orbital

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The carbanion

• The carbanion is sp3-hybridized, with the lone
  pair occupying one of the sp3-orbitals

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The methyl radical

• Similar to the carbocation, the methyl radical is
  sp2-hybridized with an electron in the p-orbital
  perpendicular to the plane.
• Make problem 2.9

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Ethane
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Rotational freedom
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The Newman projection
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Energy of the conformations

• Make problems 2.10 and 2.12

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Propane
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Conformations of butane
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Conformations of butane (II)

• Make problem 2.18

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Nomenclature
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Isomers of pentane
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Nomenclature
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Start from the longest C-chain
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Cycloalkanes
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Nomenclature
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Behavior of alkanes

• The most important interactions in alkanes are
  Vanderwaals interactions

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Problems

• Make problems 2.27, 2.28, 2.33 (no names), 2.40,
  2.41, 2.42