Heterosiklik

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Heterosiklik

  1. 1. HETEROCYCLES• Monocyclic or fused rings• Cont. one ore more ring atom ≠ C(normally O; N; S)• Aromatic and non-aromatic
  2. 2. Heterocyclic Aromatic Compounds Example of aromatic heterocyclic compounds areshown below Numbering always starts at the heteroatom2
  3. 3.  6-Membered rings (Heteroatom N)NPyridineOther examplesNQuinolineNNPyrimidineNNPyridazineRare in natureNNPyrazineNNHNH2OCytosineNQuinineH3COHONNAnt pheremoneNNHydralazineAntihypertensive drugH2NHN
  4. 4. Pyridine has an sp2hybridized nitrogen The p orbital on nitrogen is part of the aromaticsystem of the ring The nitrogen lone pair is in an sp2 orbitalorthogonal to the p orbital of the ring; theseelectrons are not part of the aromatic system The lone pair on nitrogen is available to react withprotons and so pyridine is basic
  5. 5. Pyridine as a baseN NH+ Hkebasaan piridin (pKb=8,75) < kebasaan aminaalifatik (pKb=+4)karenaelektron menyendiri berada dalam orbital sp2bukan orbital sp3NHClCH3INH Cl+ _NCH3 I+ _menjalani reaksi khasamina
  6. 6. ELECTROPHILIC SUBSTITUTION6-membered rings- N more electronegative than C- electron deficient in ring(atom C mengemban muatan positif parsial)- reactivity in electrophilic substitution(dibandingkan dengan benzena)N N N N N
  7. 7. NNENHENE+ E+ res. forms•Both C and N may react•3/5 pos. most reactive C•Not Friedel-Crafts reaction•Not coupling wit diazonium•Sulfonation, Nitration, Halogenation(brominasi berlangsung hanya padatemperatur tinggi dalam fase uap,melalui mekanisme radikal bebas)N NHNHH NO2NNO2H / NO2 H / NO2+ res. formsBenzo ring most reactiveMuch slower react. than naphthalene
  8. 8. OKSIDASICH3CO2HKMnO4kalorNNCH3CO2HKMnO4kalor
  9. 9. 6-membered rings (N menarik rapatan elektron dari cincin)N ClOMeNOMeCl+ res. formN OMe2 / 4 Pos. reactive; electron def. C, neg. charge partly on N in interm3 / 5-Pos. much less reactive (benzenoid pos.)Nucleophilic SubstitutionX Nu XNuXNuXNuNu
  10. 10. + NH2_100oCN+ NH2_100oC-H2ON NH_N NH2H2O
  11. 11. NNHNO3H2SO40oCHNO3H2SO40oCkuinolinaisokuinolinaN N+NO2NO2N N+NO2NO2•merupakan basa lemah•menjalani substitusi elektrofilik lebih mudah daripada piridin•substituen masuk pada posisi 5 dan 8
  12. 12. NNkuinolinaisokuinolinaNNNH2CH3NH2_H2OCH3LiH2OSubstitusi nukleofilikterjadi pada posisi 2 terhadap nitrogen
  13. 13.  5-Membered rings (Heteroatom N, O, S)SThiopheneNHPyrroleOThiopheneOther examplesNNHImidazoleNSThiazoleNHIndoleNHR NHRRR=HR=CO2HR=HTryptophaneR=HR=HR=OHSerotoninR=AcR=HR=OCH3MelatoninNNHNNNH2Adenine(purine der.)NNHH2NRR=CO2H: HistidineR=H: HistamineNSNNH3CHOH2NCH3Thiamin(Vit B1)
  14. 14. The nitrogen in pyrrole is sp2 hybridizedand the lone pair resides in the p orbitalThis p orbital contains two electrons andparticipates in the aromatic systemThe lone pair of pyrrole is part of thearomatic system and not available forprotonation; pyrrole is therefore not basicChapter 14 14
  15. 15.  In furan and thiophene an electronpair on the heteroatom is also in ap orbital which is part of thearomatic system
  16. 16. 5-membered rings - electron richX+ EXEH XEH XEH X EX+ EXEHXEHX EReact. in -position generally preferred, moreresonance structuresReact.: Pyrrole > thiophene > furan•karena atom N menyumbang 2 elektron ke awanpi aromatik, atom N menjadi deficient electron,tidak bersifat basa•cincin kaya elektron
  17. 17. NHNHNHSO3HNO2SO3piridinHNO3(CH3CO)2OSUBSTITUSI ELEKTROFILIKtidak menjalani reaksi substitusi nukleofilik
  18. 18. Nucleosides, Nucleotides, Nucleic acids (DNA; RNA)DNA basesDNA Nucleosides2-DeoxyribosidesRNA basesHNNOOThymidineNNNH2ODeoxycytosine DeoxyadenosineNN NNNH2HNN NNOH2NO O O OOH OH OH OHHO HO HO HODeoxyguanoosineHNNHOOThyminNNHNH2OCytosin AdenineNN NHNNH2GuanineHNN NHNOH2NHNNHOOUracilCytosin Adenine GuanineRNA NucleosidesRibosidesHNNOOUrinineCytosineAdenosineOOHHOGuanoosineOH
  19. 19. NucleotidesOOXHOBPOOXOBPOOOHOXOBOO53Double -helix(DNA)A-T and G-C Base pairsNNOO CH3HNNN HHNNNNONNNONNHNHHHH
  20. 20. PORFIRINA : cincin pirolB : cincin porfirinC : protoporfirin IX
  21. 21. ALKALOID :senyawa yang diambil dari jaringantumbuhan yang mengandung nitrogen dalamstrukturnya dan larut dalam air nikotina morfina kodeina heroin dekstrometorfan atropina skopolamina kokaina

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