Transcription of Heterocyclic compounds (1)
1 1 Heterocyclic compounds (1)ByDr. GhassanQaisAliHeterocyclic compounds2 Introduction:Studentswillbefamiliarwithc arbocycliccompounds,suchascyclohexaneand benzene, , , ,sulfurornitrogen,butmanyotherelementsca nfunctioninthisway,includingboron, , ,manyheterocyclesretainthesenames;aselec tionofcommonfive-andsix-memberedheterocy clesthatcontainoneoxygen, Cycliccompoundshavingasringmembersatomso fatleasttwodifferentelements, ,1,2-thiazole. Any of a class of organic compounds whose molecules contain one or more rings of atoms with at least one atom (the heteroatom) being an element other than carbon, most frequently oxygen, nitrogen, or ,nucleicacids,thechemicalsubstancesthatc arrythegeneticinformationcontrollinginhe ritance,consistoflongchainsofheterocycli cunitsheldtogether)DNAiscomposedofhetero cyclicbases-pyrimidinesandpurines(.
2 Manynaturallyoccurringpigments,vitamins, ,bothsyntheticandnatural, ,fungicides,herbicides, ,developers,antioxidants, derivatives and classification Heterocyclic derivatives as a group, can be divided into two broad areas:aromatic and non-aromatic. (note : aromatic system must have 4n+2 -electron)1) the 1, five-membered rings are shown below, the derivative furan (1) is aromatic, while tetrahydrofuran (2), dihydrofuran-2-one (3) are not aromatic, Why?.2) The six-membered rings below, pyridine is aromatic (5), while piperidine(6), piperidin-2-one (7) are not aromatic, why? Most heterocycles have the same chemistry as their open-chain counterparts particularly when the ring is general : Heterocyclic is the largest and most varied family of organic compounds , Heterocyclic system can be 3, 4, 5, 6, 7 membered rings 7 Heterocyclic compounds are cyclic compounds which contains one/more atoms of other elements along with carbon Of Heteroatom: Heteroatomsarethosewhichcontainsanatomot herthancarbonsuchasnitrogen,sulphur, Of Heterocyclic compounds .
3 89in addition to a fused rings (two rings joined at two adjacent atoms)9H-When Is A Molecule Aromatic? For a molecule to be aromatic it must: Be cyclic and conjugated Have a p-orbital on every atom in ring Be planar and All bond angles are 120 , all carbon atoms are sp2-hybridized Posses 4n+2 p electrons (n = any integer)benzenenaphthalene+cyclopropenyl cation[14]-AnnuleneCLASSIFICATION: Depending upon the size of Heterocyclic ring, they are classified into different membered Heterocyclic compounds : OoxiraneHNaziridine2-Four membered Heterocyclic compounds :Ooxetan3-Five membered Heterocyclic compounds .
4 NHNpyrazoleSNthiazoleONisooxazoleOfuranN HpyrroleNNNHN tetrazole4-Six membered Heterocyclic compounds :NPyridineNHpiperidineSNthiazin e5-Seven membered Heterocyclic compounds :Sthiepine6-Eight membered Heterocyclic compounds :Nazocine7-Fused Heterocyclic compounds :NquinolineNisoquinolineNHindol e8-Condensed ring systems:NHNbenzimidazoleNOMENCLATURE Systematicnomenclaturesystemisusedfornam ing3-10 HuckelRule Huckelrule statesthataromaticityisobtainedinthecycl icconjugatedandplanersystemcontaining(4n +2) Heterocyclic compounds are named by fusing the following rules: 1-Combination of prefixes with stem 2-The prefixes for different heteroatoms.
5 3-stem may be divided into two subdivided:a) Basic term represent of ring ) Suffixes represent of the end for different :HeteroatomSymbolValencePrefix1 Oxygeno2oxa2 Sulphurs2 Thia3 NitrogenN3 Aza6 PhosphorusP3 Phospha7 ArsenicAs3 Arsa8 AntimonySb3 Siba9 BismuthBi3 Bisma10 SiliconSi4 Silica11 GeraniumGe4 Germa12 TinSn4 Stanna13 LeadPb4 Plumba14 BoranB3 Bora15 MercuryHg2 Mercura17 Stem for different ringsRules that have to be considered while giving names to the Heterocyclic compounds :Thenamesofthemonocycliccompoun dsarederivedbyaprefixindicatingthenature ofheteroatomspresentandintroducingoromit tingthe a :HNAziridine123 Ooxetan1234 Whentwoaremoreofthesameheteroatomsarepre sent,theprefixes di,tri ,3-dioxolane12453 Iftheheteroatomsaredifferenttheyarenamed intheorderof O,S,N,P,Si :-Thestateofhydrogenationisindicatedinth esuffixorbytheprefixesdihydro,tetrahydro etcorbyprefixingthenameoftheparentunsatu ratedcompoundwiththesymbol H :SNHS2H,6H-1,5, :Nquinolineor2,3-benzopyridine2122 Notes.
6 1-232-243-254-2627 Importance to Life and ,andtheirmetabolitesmaybeusedtoadvantage ;forexample,astoxinstowardoffpredators, , ,thepairedbasesfoundinRNAandDNAarehetero cycles, (nicotine,pyridoxine,cocaineandmorphine) andtwosyntheticcompounds(nifedipineandpa raquat).32
