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Heterocycles (McM chapt 28)

Heterocycles (McM chapt 28). Monocyclic or fused rings Cont. one ore more ring atom ≠ C (normally O; N; S) Aromatic , partly saturated or saturated ring(s). 5-Membered rings (Heteroatom N, O, S). Criteria for Aromaticity (Hückel) (Monocyclic) ring Planar

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Heterocycles (McM chapt 28)

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  1. Heterocycles (McM chapt 28) • Monocyclic or fused rings • Cont. one ore more ring atom ≠ C (normally O; N; S) • Aromatic, partly saturated or saturated ring(s) 5-Membered rings (Heteroatom N, O, S)

  2. Criteria for Aromaticity (Hückel) (Monocyclic) ring Planar No of p-electrons in conjugation 4n+2 (n: 0, 1, 2,....)

  3. 5-membered rings - electron rich - reactive i E-fil. Ar subst. React. in a-position generally preferred Selectivity not always good React.: Pyrrole > thiophene > furan

  4. 6-Membered rings (Heteroatom N)

  5. Pyridine as a base pKa: 5.2 sp2 N less basic than sp3

  6. Electrophilic Reaction on Carbon: E-phil. Ar. Subs. 6-membered rings - electron deficient -  reactivity • Both C and N may react • 3/5 pos. most reactive C • Diazines less reactive • Sulfonation, Nitration, halogenatil • Not FC react. Benzo ring most reactive Much slower react. than naphthalene

  7. Nucleophilic Aromatic Substitution • SNAr • SN1: Via arylic cation • Benzyne • SRN1: Involves radicals • VNS: Vicarious nucl. Subst. 6-membered rings - electron deficient - reactive in Nu-fil. Ar subst. 2 / 4 Pos. reactive; electron def. C, neg. charge partly on N in intermed 3 / 5-Pos. much less reactive (benzenoid pos.)

  8. Nucleosides, Nucleotides, Nucleic acids (DNA; RNA) DNA bases RNA bases DNA Nucleosides RNA Nucleosides Ribosides 2-Deoxyribosides

  9. Nucleotides A-T and G-C Base pairs Double a-helix (DNA)

  10. Nucleotide sequence in DNA - genetic information

  11. DNA helicases: Unwinding DNA binding proteins: Prevents winding back DNA primase: formation of DNA/RNA primer (from free nucleosides in cell) DNA polymerase: Catalyse elongation of new strand (5’ - 3’) Lagging strand: DNA ligase: Connects Okasaki fragments

  12. Transcription: DNA - RNA

  13. Translation: RNA - Protein 3 RNA bases coding for one AA (see Table 28.1) Protein synthesis occurs at ribosomes

  14. DNA / RNA Synthesis: Protecting groups and activating groups (cf. peptide synth)

  15. The Polymerase Chain Reaction (PCR, 1986) technique for quickly "cloning”(make many copies of) a particular piece of DNA in the test tube (rather than in living cells like E. coli). primers: short oligonucleotides (ca 20 nucleotides) precisely complementary to the sequence at the 3' end of each strand of the DNA Tac DNA polymerase: Heat stable enzyme from Thermus aquaticus (bacteria) in hot springs Yellowstone Nat. Park

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