CHAPTER 25 Heterocycles: Heteroatoms in Cyclic Organic Compounds 25-1 Naming the Heterocycles kpl-forphosphoroug 分 1 CHAPTER 25 Heterocycles: Heteroatoms in Cyclic Organic Compounds Most physiologically active compounds owe their biological properties to the presence of heteroatoms, mainly in the form of heterocycles. 25-1 Naming the Heterocycles Saturated heterocycles will be treated as derivatives of the related carbocycles. A prefix will be used to denote the presence and identity of the heteroatom: aza- for nitrogen oxa- for oxygen thia- for sulfur phospha- for phosphorous etc. The substituent locations will be denoted by numbering the ring atoms, starting at the heteroatom. Hantzsch-Widman naming system 10 -ecine -ecin -ecane 9 -onine -onin -onane 8 -ocine perhydro- -ocin -ocane 7 -epine prefix -epine -epane 6 -ine -ine -ane 5 -ole olidine -ole -olane 4 -ete -etidine -ete -etane 3 -irine -iridine -irene -irane Ring unsaturated saturated unsaturated saturated member Nonnitrogen￾containing Nitrogen￾containing aza- for nitrogen oxa- for oxygen thia- for sulfur phospha- for phosphorous Boro- for boron