instance_of isothiazole
An isothiazole , or ___MASK98___ , 2 - thiazole , is a type of ___MASK48___ containing a five - membered aromatic ring that consists of three carbon atoms , one nitrogen atom , and one sulfur atom . Isothiazole is a member of a class of compounds known as azoles . In contrast to the isomeric thiazole , the two heteroatoms are in adjacent positions . The ring structure of isothiazole is incorporated into larger compounds with biological activity such as the pharmaceutical drugs ziprasidone and perospirone . Pyridine is a basic heterocyclic ___MASK48___ with the chemical formula CHN . It is structurally related to benzene , with one methine group (= CH ) replaced by a nitrogen atom . The pyridine ring occurs in many important compounds , including azines and the vitamins niacin and pyridoxine . A ___MASK62___ or ___MASK74___ structure is a cyclic compound that has atoms of at least two different elements as members of its ___MASK74___ ( s ). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis , properties , and applications of these heterocycles . Carbon ( from " coal ") is a ___MASK92___ element with symbol C and atomic number 6 . It is nonmetallic and tetravalent  making four electrons available to form covalent ___MASK92___ bonds . Three isotopes occur naturally , C and C being stable , while C is a radioactive isotope , decaying with a half - life of about 5 , 730 years . Carbon is one of the few elements known since antiquity . An ___MASK48___ is virtually any ___MASK46___ that contains carbon , although a consensus definition remains elusive and likely arbitrary . Organic compounds are rare terrestrially , but of central importance because all known life is based on organic compounds . The most basic petrochemicals are considered the building blocks of organic chemistry . Pyrazoline is a heterocyclic ___MASK46___ with the molecular formula CHN . Azoles are a ___MASK67___ of ___MASK36___ - membered heterocyclic compounds containing a nitrogen atom and at least one other non - carbon atom ( i . e . nitrogen , sulfur , or oxygen ) as part of the ring . Their names originate from the Hantzsch  Widman ___MASK76___ . The parent compounds are aromatic and have two double bonds ; there are successively reduced analogs ( azolines and azolidines ) with fewer . One , and only one , lone pair of electrons from each heteroatom in the ring is part of the aromatic bonding in an azole . Names of azoles maintain the prefix upon reduction ( e . g ., pyrazoline , pyrazolidine ). The numbering of ring atoms in azoles starts with the heteroatom that is not part of a double bond , and then proceeds towards the other heteroatom . Thiazole , or ___MASK98___ , 3 - thiazole , is a heterocyclic compound that contains both sulfur and nitrogen ; the term ' thiazole ' also refers to a large family of derivatives . Thiazole itself is a pale yellow liquid with a pyridine - like odor and the molecular formula CHNS . The thiazole ring is notable as a component of the vitamin thiamine ( B ). A ___MASK46___ ( or just compound if used in the context of chemistry ) is an entity consisting of two or more atoms , at least two from different elements , which associate via chemical bonds . There are four types of compounds , depending on how the constituent atoms are held together : molecules held together by covalent bonds , ionic compounds held together by ionic bonds , intermetallic compounds held together by metallic bonds , and certain complexes held together by coordinate covalent bonds . Many chemical compounds have a unique numerical identifier assigned by the Chemical Abstracts Service ( CAS ): its CAS number . A ___MASK53___ is an ___MASK48___ and a vital ___MASK66___ that an ___MASK59___ requires in limited amounts . An organic ___MASK46___ ( or related set of compounds ) is called a ___MASK53___ when the ___MASK59___ cannot synthesize the compound in sufficient quantities , and it must be obtained through the diet ; thus , the term " ___MASK53___ " is conditional upon the circumstances and the particular ___MASK59___ . For example , ascorbic acid ( one form of ___MASK53___ C ) is a ___MASK53___ for humans , but not for most other animal organisms . Supplementation is important for the treatment of certain health problems , but there is little evidence of nutritional benefit when used by otherwise healthy people .