Molecular formula
C20H18FN3O2S
81 compounds have this formula on CompoundList.
- Molar mass
- 383.44g/mol
- Monoisotopic mass
- 383.1104Da
- Atoms
- 45
- Elements
- 6
- Rings plus double bonds
- 13
The formula C20H18FN3O2S describes a molecule made of 20 carbon atoms, 18 hydrogen atoms, 1 fluorine atom, 3 nitrogen atoms, 2 oxygen atoms and 1 sulfur atom. It is written in Hill notation: carbon first, then hydrogen, then the other elements in alphabetical order. The formula tells you which atoms are present, not how they are connected, which is why several different chemicals can share it.
Elemental composition
- C Carbon × 2062.65%12.011 × 20 = 240.220 g/mol
- H Hydrogen × 184.73%1.008 × 18 = 18.144 g/mol
- F Fluorine × 14.95%18.998 × 1 = 18.998 g/mol
- N Nitrogen × 310.96%14.007 × 3 = 42.021 g/mol
- O Oxygen × 28.34%15.999 × 2 = 31.998 g/mol
- S Sulfur × 18.36%32.06 × 1 = 32.060 g/mol
Look up another formula
Compounds with the formula C20H18FN3O2S
Isomers we list, best known first. Open one to see its structure, properties, safety data and suppliers.
Showing 1 to 81 of 81 compounds
3-(1,5-Dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-2-(4-fluorophenyl)-1,3-thiazolidin-4-one
CAS 128317-50-0C20H18FN3O2S
![2-(4-Fluorophenyl)-N-(5-oxido-2-(o-tolyl)-4,6-dihydro-2H-thieno[3,4-c]pyrazol-3-yl)acetamide chemical structure, C20H18FN3O2S, CAS 958711-08-5](/s/KVNZXQJMTRJLDZ-UHFFFAOYSA-N.svg)
2-(4-Fluorophenyl)-N-(5-oxido-2-(o-tolyl)-4,6-dihydro-2H-thieno[3,4-c]pyrazol-3-yl)acetamide
CAS 958711-08-5C20H18FN3O2S
![N-[2-(4-Fluorophenyl)-5-oxo-4,6-dihydrothieno[3,4-c]pyrazol-3-yl]-2-(3-methylphenyl)acetamide chemical structure, C20H18FN3O2S, CAS 1008921-15-0](/s/NVGQLCGGLYRMMM-UHFFFAOYSA-N.svg)
N-[2-(4-Fluorophenyl)-5-oxo-4,6-dihydrothieno[3,4-c]pyrazol-3-yl]-2-(3-methylphenyl)acetamide
CAS 1008921-15-0C20H18FN3O2S
![4-Ethoxy-N-[2-(4-fluorophenyl)-4,6-dihydrothieno[3,4-c]pyrazol-3-yl]benzamide chemical structure, C20H18FN3O2S, CAS 450342-99-1](/s/KSLQWQYQHOUSTJ-UHFFFAOYSA-N.svg)
4-Ethoxy-N-[2-(4-fluorophenyl)-4,6-dihydrothieno[3,4-c]pyrazol-3-yl]benzamide
CAS 450342-99-1C20H18FN3O2S
![N-[2-(4-Fluorophenyl)-5-oxo-4,6-dihydrothieno[3,4-c]pyrazol-3-yl]-3,4-dimethylbenzamide chemical structure, C20H18FN3O2S, CAS 1007550-69-7](/s/BLMPQZDBKSOXPN-UHFFFAOYSA-N.svg)
N-[2-(4-Fluorophenyl)-5-oxo-4,6-dihydrothieno[3,4-c]pyrazol-3-yl]-3,4-dimethylbenzamide
CAS 1007550-69-7C20H18FN3O2S
![3-Amino-N-(4-fluorophenyl)-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydrothieno[2,3-b]quinoline-2-carboxamide chemical structure, C20H18FN3O2S, CAS 442556-63-0](/s/JAPLRDOJYMOJHP-UHFFFAOYSA-N.svg)
3-Amino-N-(4-fluorophenyl)-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydrothieno[2,3-b]quinoline-2-carboxamide
CAS 442556-63-0C20H18FN3O2S
![2-Ethoxy-N-(2-(4-fluorophenyl)-4,6-dihydro-2H-thieno[3,4-c]pyrazol-3-yl)benzamide chemical structure, C20H18FN3O2S, CAS 450342-98-0](/s/LOSFMTQEXYEOQR-UHFFFAOYSA-N.svg)
2-Ethoxy-N-(2-(4-fluorophenyl)-4,6-dihydro-2H-thieno[3,4-c]pyrazol-3-yl)benzamide
CAS 450342-98-0C20H18FN3O2S
![N-(4-Acetylphenyl)-2-[1-[(4-fluorophenyl)methyl]imidazol-2-yl]sulfanylacetamide chemical structure, C20H18FN3O2S, CAS 869346-28-1](/s/MGASOJAZKPUDJP-UHFFFAOYSA-N.svg)
N-(4-Acetylphenyl)-2-[1-[(4-fluorophenyl)methyl]imidazol-2-yl]sulfanylacetamide
CAS 869346-28-1C20H18FN3O2S
![N-(4-Fluorophenyl)-1-methyl-2-[(2-methylphenyl)methylsulfanyl]-6-oxopyrimidine-5-carboxamide chemical structure, C20H18FN3O2S, CAS 891102-11-7](/s/MTJHPAALKBHYAQ-UHFFFAOYSA-N.svg)
N-(4-Fluorophenyl)-1-methyl-2-[(2-methylphenyl)methylsulfanyl]-6-oxopyrimidine-5-carboxamide
CAS 891102-11-7C20H18FN3O2S
N-(4-Fluorobenzyl)-2-((6-(3-methoxyphenyl)pyridazin-3-yl)thio)acetamide
CAS 872695-24-4C20H18FN3O2S
![(R)-N-(4-Amino-4'-fluoro-[1,1'-biphenyl]-3-yl)-4-(S-methylsulfonimidoyl)benzamide chemical structure, C20H18FN3O2S, CAS 2935964-98-8](/s/JPFMYSJUFUEHBI-HHHXNRCGSA-N.svg)
(R)-N-(4-Amino-4'-fluoro-[1,1'-biphenyl]-3-yl)-4-(S-methylsulfonimidoyl)benzamide
CAS 2935964-98-8C20H18FN3O2S
(E)-3-(((3-(4-Fluorophenyl)-1-phenyl-1H-pyrazol-4-yl)methylene)amino)tetrahydrothiophene 1,1-dioxide
CAS 384802-91-9C20H18FN3O2S
![1-Fluoro-3-[[2-[(1E)-4-[6-(methylamino)-3-pyridinyl]-1-buten-3-yn-1-yl]-6-benzothiazolyl]oxy]-2-propanol chemical structure, C20H18FN3O2S, CAS 1565797-17-2](/s/GTSLERAOSMSMIY-HWKANZROSA-N.svg)
1-Fluoro-3-[[2-[(1E)-4-[6-(methylamino)-3-pyridinyl]-1-buten-3-yn-1-yl]-6-benzothiazolyl]oxy]-2-propanol
CAS 1565797-17-2C20H18FN3O2S
N-(4-Fluorophenyl)-2-(morpholin-4-yl)-4-phenyl-1,3-thiazole-5-carboxamide
CAS 862391-34-2C20H18FN3O2S
![N-[2-(2,4-Dimethylphenyl)-5-oxo-4,6-dihydrothieno[3,4-c]pyrazol-3-yl]-3-fluorobenzamide chemical structure, C20H18FN3O2S, CAS 1007550-67-5](/s/UTXWUSUQDYUTNK-UHFFFAOYSA-N.svg)
N-[2-(2,4-Dimethylphenyl)-5-oxo-4,6-dihydrothieno[3,4-c]pyrazol-3-yl]-3-fluorobenzamide
CAS 1007550-67-5C20H18FN3O2S
![2-(4-Fluorophenyl)-N-(2-(4-methoxyphenyl)-4,6-dihydro-2H-thieno[3,4-c]pyrazol-3-yl)acetamide chemical structure, C20H18FN3O2S, CAS 476458-26-1](/s/ZSHLSRHBCVCJIG-UHFFFAOYSA-N.svg)
2-(4-Fluorophenyl)-N-(2-(4-methoxyphenyl)-4,6-dihydro-2H-thieno[3,4-c]pyrazol-3-yl)acetamide
CAS 476458-26-1C20H18FN3O2S
![N-[2-Amino-5-(4-fluorophenyl)phenyl]-4-(methylsulfonimidoyl)benzamide chemical structure, C20H18FN3O2S, CAS 2935964-93-3](/s/JPFMYSJUFUEHBI-UHFFFAOYSA-N.svg)
N-[2-Amino-5-(4-fluorophenyl)phenyl]-4-(methylsulfonimidoyl)benzamide
CAS 2935964-93-3C20H18FN3O2S
![N-(2-Ethylphenyl)-2-{[4-(4-fluorophenyl)-3-oxo-3,4-dihydropyrazin-2-yl]sulfanyl}acetamide chemical structure, C20H18FN3O2S, CAS 895104-08-2](/s/BJDKZFQDNCRINS-UHFFFAOYSA-N.svg)
N-(2-Ethylphenyl)-2-{[4-(4-fluorophenyl)-3-oxo-3,4-dihydropyrazin-2-yl]sulfanyl}acetamide
CAS 895104-08-2C20H18FN3O2S
![N-(3,5-Dimethylphenyl)-2-{[4-(3-fluorophenyl)-3-oxo-3,4-dihydropyrazin-2-yl]sulfanyl}acetamide chemical structure, C20H18FN3O2S, CAS 899998-65-3](/s/XCRRDVDVRUBIQM-UHFFFAOYSA-N.svg)
N-(3,5-Dimethylphenyl)-2-{[4-(3-fluorophenyl)-3-oxo-3,4-dihydropyrazin-2-yl]sulfanyl}acetamide
CAS 899998-65-3C20H18FN3O2S
![6-(4-Fluorobenzyl)-4-(4-(methylthio)phenyl)-3,4,6,7-tetrahydro-1H-pyrrolo[3,4-d]pyrimidine-2,5-dione chemical structure, C20H18FN3O2S, CAS 1021060-70-7](/s/CJDMMMADWPSHTP-UHFFFAOYSA-N.svg)
6-(4-Fluorobenzyl)-4-(4-(methylthio)phenyl)-3,4,6,7-tetrahydro-1H-pyrrolo[3,4-d]pyrimidine-2,5-dione
CAS 1021060-70-7C20H18FN3O2S
![2-(Allylthio)-5-(4-fluorophenyl)-7,8,9,10-tetrahydropyrimido[4,5-b]quinoline-4,6(3H,5H)-dione chemical structure, C20H18FN3O2S, CAS 627045-73-2](/s/HWNLPFWHQYQDDJ-UHFFFAOYSA-N.svg)
2-(Allylthio)-5-(4-fluorophenyl)-7,8,9,10-tetrahydropyrimido[4,5-b]quinoline-4,6(3H,5H)-dione
CAS 627045-73-2C20H18FN3O2S
(S)-TNG260
C20H18FN3O2S
![2-[(4-Fluorophenyl)methylsulfanyl]-3-(2-methoxyethyl)-5H-pyrimido[5,4-b]indol-4-one chemical structure, C20H18FN3O2S, CAS 888440-70-8](/s/URUOICSVXPMYTQ-UHFFFAOYSA-N.svg)
2-[(4-Fluorophenyl)methylsulfanyl]-3-(2-methoxyethyl)-5H-pyrimido[5,4-b]indol-4-one
CAS 888440-70-8C20H18FN3O2S
![N-(4-Ethylphenyl)-2-{[4-(4-fluorophenyl)-3-oxo-3,4-dihydropyrazin-2-yl]sulfanyl}acetamide chemical structure, C20H18FN3O2S, CAS 899965-30-1](/s/FXYSJCQVSZASDP-UHFFFAOYSA-N.svg)
N-(4-Ethylphenyl)-2-{[4-(4-fluorophenyl)-3-oxo-3,4-dihydropyrazin-2-yl]sulfanyl}acetamide
CAS 899965-30-1C20H18FN3O2S
- (5Z)-5-[[1-(4-Fluorophenyl)-2,5-dimethylpyrrol-3-yl]methylidene]-1-prop-2-enyl-2-sulfanylidene-1,3-diazinane-4,6-dione340311-34-4C20H18FN3O2S
- N-[2-(4-Fluorophenyl)-5-oxo-4,6-dihydrothieno[3,4-c]pyrazol-3-yl]-3,5-dimethylbenzamide1007475-46-8C20H18FN3O2S
- N-{2-[2-(4-Fluorophenyl)-4-methyl-1,3-thiazol-5-yl]ethyl}-N'-phenylethanediamide895802-35-4C20H18FN3O2S
- N-{2-[2-(3-Fluorophenyl)-4-methyl-1,3-thiazol-5-yl]ethyl}-N'-phenylethanediamide895804-17-8C20H18FN3O2S
- N-{2-[2-(3-Fluorophenyl)-1,3-thiazol-4-yl]ethyl}-N'-(4-methylphenyl)ethanediamide895783-68-3C20H18FN3O2S
- N-{2-[2-(3-Fluorophenyl)-1,3-thiazol-4-yl]ethyl}-N'-(3-methylphenyl)ethanediamide895783-78-5C20H18FN3O2S
- N-{2-[2-(3-Fluorophenyl)-1,3-thiazol-4-yl]ethyl}-N'-(2-methylphenyl)ethanediamide895784-55-1C20H18FN3O2S
- N1-(4-fluorophenyl)-N2-(2-(2-(p-tolyl)thiazol-4-yl)ethyl)oxalamide896378-00-0C20H18FN3O2S
- 2-[4-(4-Fluorophenyl)-3-oxopyrazin-2-yl]sulfanyl-N-[(4-methylphenyl)methyl]acetamide942034-28-8C20H18FN3O2S
- N-(1,3-Benzothiazol-2-yl)-1-(4-fluorobenzoyl)piperidine-4-carboxamide926434-48-2C20H18FN3O2S
- N-(2,4-Dimethylphenyl)-2-((4-(4-fluorophenyl)-3-oxo-3,4-dihydropyrazin-2-yl)thio)acetamide895104-45-7C20H18FN3O2S
- N-(2,4-Dimethylphenyl)-2-((4-(3-fluorophenyl)-3-oxo-3,4-dihydropyrazin-2-yl)thio)acetamide899998-63-1C20H18FN3O2S
- N-(3,5-Dimethylphenyl)-2-((4-(4-fluorophenyl)-3-oxo-3,4-dihydropyrazin-2-yl)thio)acetamide899949-63-4C20H18FN3O2S
- N-(2,5-Dimethylphenyl)-2-((4-(4-fluorophenyl)-3-oxo-3,4-dihydropyrazin-2-yl)thio)acetamide895104-69-5C20H18FN3O2S
- N-(4-(3-((3-Fluoro-4-methylphenyl)amino)-3-oxopropyl)thiazol-2-yl)benzamide1021256-72-3C20H18FN3O2S
- (E)-1-(4-(5-(4-Fluorophenyl)-1,3,4-oxadiazol-2-yl)piperidin-1-yl)-3-(thiophen-2-yl)prop-2-en-1-one1212782-93-8C20H18FN3O2S
- (E)-1-(3-(5-(2-Fluorophenyl)-1,3,4-thiadiazol-2-yl)piperidin-1-yl)-3-(furan-2-yl)prop-2-en-1-one1351663-88-1C20H18FN3O2S
- (7-(2-Fluorophenyl)-1,4-thiazepan-4-yl)(5-(pyridin-3-yl)isoxazol-3-yl)methanone1706092-18-3C20H18FN3O2S
- N-({[2-(Benzylsulfanyl)-6-methylpyrimidin-4-yl]oxy}methyl)-4-fluorobenzamide637321-95-0C20H18FN3O2S
- (5Z)-2-[4-(2-Fluorophenyl)piperazin-1-yl]-5-(4-hydroxybenzylidene)-1,3-thiazol-4(5H)-one577999-82-7C20H18FN3O2S
- N-(2-(4-Fluorophenyl)-5-oxido-4,6-dihydro-2H-thieno[3,4-c]pyrazol-3-yl)-3-phenylpropanamide1007476-19-8C20H18FN3O2S
- 2-[6-(4-Fluorophenyl)pyridazin-3-yl]sulfanyl-N-(2-methoxy-5-methylphenyl)acetamide896048-33-2C20H18FN3O2S
- N-(3-Fluoro-4-methylphenyl)-2-[6-(3-methoxyphenyl)pyridazin-3-yl]sulfanylacetamide896049-07-3C20H18FN3O2S
- N1-(4-fluorophenyl)-N2-(2-(4-methyl-2-phenylthiazol-5-yl)ethyl)oxalamide894010-54-9C20H18FN3O2S
- N1-(3-fluorophenyl)-N2-(2-(4-methyl-2-phenylthiazol-5-yl)ethyl)oxalamide894010-61-8C20H18FN3O2S
- N-Benzyl-2-[4-(3-fluoro-4-methylphenyl)-3-oxopyrazin-2-yl]sulfanylacetamide899944-52-6C20H18FN3O2S
- 2-[4-(3-Fluoro-4-methylphenyl)-3-oxopyrazin-2-yl]sulfanyl-N-(4-methylphenyl)acetamide899759-17-2C20H18FN3O2S
- 2-(2-Fluorophenoxy)-N-[2-(2-methylphenyl)-4,6-dihydrothieno[3,4-c]pyrazol-3-yl]acetamide893944-32-6C20H18FN3O2S
- 2-[4-(3,4-Dimethylphenyl)-3-oxopyrazin-2-yl]sulfanyl-N-(2-fluorophenyl)acetamide941929-50-6C20H18FN3O2S
- N-(3-Fluoro-4-methylphenyl)-2-((3-oxo-4-(p-tolyl)-3,4-dihydropyrazin-2-yl)thio)acetamide941935-39-3C20H18FN3O2S
- N-(1,3-Benzothiazol-2-yl)-1-(2-fluorobenzoyl)piperidine-4-carboxamide942893-59-6C20H18FN3O2S
- N-(1,3-Benzothiazol-2-yl)-1-(3-fluorobenzoyl)piperidine-4-carboxamide945335-43-3C20H18FN3O2S
- 2-((4-(3-Fluoro-4-methylphenyl)-3-oxo-3,4-dihydropyrazin-2-yl)thio)-N-(o-tolyl)acetamide900006-79-3C20H18FN3O2S
- 2-((4-(3-Fluoro-4-methylphenyl)-3-oxo-3,4-dihydropyrazin-2-yl)thio)-N-(m-tolyl)acetamide899759-22-9C20H18FN3O2S
- 2-(4-(3-(2-Fluorophenyl)ureido)phenyl)-N-(thiophen-2-ylmethyl)acetamide1211294-34-6C20H18FN3O2S
- 2-(Cyclopentylsulfanyl)-1-(4-fluorophenyl)-5-(3-nitrophenyl)-1H-imidazole1234974-92-5C20H18FN3O2S
- N-(2-Fluorobenzyl)-2-{3-[4-(methylsulfanyl)phenyl]-6-oxopyridazin-1(6H)-yl}acetamide1282118-56-2C20H18FN3O2S
- N-(3-Fluorobenzyl)-2-{3-[4-(methylsulfanyl)phenyl]-6-oxopyridazin-1(6H)-yl}acetamide1282098-80-9C20H18FN3O2S
- N-[2-(3-Fluorophenyl)cyclopropyl]-2-(furan-2-yl)-4-methyl-6-(methylsulfanyl)pyrimidine-5-carboxamide1424563-20-1C20H18FN3O2S
- N-(3-(2-((2-Fluorophenyl)amino)thiazol-4-yl)phenyl)tetrahydrofuran-3-carboxamide1797366-84-7C20H18FN3O2S
- 2-(2-(Ethylthio)benzoyl)-8-fluoro-3,4-dihydro-1H-dipyrido[1,2-a:4',3'-d]pyrimidin-11(2H)-one2034533-36-1C20H18FN3O2S
- (4-(4-Fluorophenyl)piperazin-1-yl)(4-(thiazol-2-yloxy)phenyl)methanone2034322-63-7C20H18FN3O2S
- 2-(2-(Benzylthio)acetyl)-8-fluoro-3,4-dihydro-1H-dipyrido[1,2-a:4',3'-d]pyrimidin-11(2H)-one2034507-31-6C20H18FN3O2S
- 8-Fluoro-2-(3-(phenylthio)propanoyl)-3,4-dihydro-1H-dipyrido[1,2-a:4',3'-d]pyrimidin-11(2H)-one2034533-61-2C20H18FN3O2S
- 2-((4-Fluorophenyl)thio)-1-(3-(5-phenyl-1,2,4-oxadiazol-3-yl)pyrrolidin-1-yl)ethanone2034416-24-3C20H18FN3O2S
- 1-(3-(1,2,4-Oxadiazol-3-yl)-4-phenylpyrrolidin-1-yl)-2-((4-fluorophenyl)thio)ethanone2034374-25-7C20H18FN3O2S
- 1-{4'-Fluoro-[1,1'-biphenyl]-4-carbonyl}-4-(1,3,4-thiadiazol-2-yloxy)piperidine2177366-32-2C20H18FN3O2S
- 2-[4-(3,5-Dimethylphenyl)-3-oxopyrazin-2-yl]sulfanyl-N-(4-fluorophenyl)acetamide895108-82-4C20H18FN3O2S
- 2-[4-(3,5-Dimethylphenyl)-3-oxopyrazin-2-yl]sulfanyl-N-(2-fluorophenyl)acetamide895109-42-9C20H18FN3O2S
- N-(2,5-Dimethylphenyl)-2-{[4-(3-fluorophenyl)-3-oxo-3,4-dihydropyrazin-2-yl]sulfanyl}acetamide899998-67-5C20H18FN3O2S
- 2-{[2-(3-Fluorophenyl)-6-methylpyrimidin-4-yl]sulfanyl}-N-(3-methoxyphenyl)acetamide1326807-12-8C20H18FN3O2S
- 1-(18F)Fluoranyl-3-[[2-[(E)-4-[6-(methylamino)pyridin-3-yl]but-1-en-3-ynyl]-1,3-benzothiazol-6-yl]oxy]propan-2-ol1565797-58-1C20H18FN3O2S
- 2-(2-{[(4-Fluorophenyl)methyl]sulfanyl}-6-oxo-1,6-dihydropyrimidin-4-yl)-N-(3-methylphenyl)acetamide1171611-50-9C20H18FN3O2S
- 2-(2-{[(2-Fluorophenyl)methyl]sulfanyl}-6-oxo-1,6-dihydropyrimidin-4-yl)-N-(3-methylphenyl)acetamide1172728-65-2C20H18FN3O2S
- 2-(2-{[(2-Fluorophenyl)methyl]sulfanyl}-6-oxo-1,6-dihydropyrimidin-4-yl)-N-(4-methylphenyl)acetamide1170543-13-1C20H18FN3O2S
- 1-Benzyl-4-(5-{[(3-fluorophenyl)methyl]sulfanyl}-1,3,4-oxadiazol-2-yl)pyrrolidin-2-one3054427-52-7C20H18FN3O2S
- 1-Benzyl-4-(5-{[(2-fluorophenyl)methyl]sulfanyl}-1,3,4-oxadiazol-2-yl)pyrrolidin-2-one3054569-69-3C20H18FN3O2S
Frequently asked questions
What is the molar mass of C20H18FN3O2S?
The molar mass of C20H18FN3O2S is 383.44 g/mol, calculated from standard atomic weights for 20 carbon atoms, 18 hydrogen atoms, 1 fluorine atom, 3 nitrogen atoms, 2 oxygen atoms and 1 sulfur atom. The monoisotopic mass is 383.1104 Da.
How many compounds have the formula C20H18FN3O2S?
CompoundList lists 81 compounds with the molecular formula C20H18FN3O2S, including 3-(1,5-Dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-2-(4-fluorophenyl)-1,3-thiazolidin-4-one, 2-(4-Fluorophenyl)-N-(5-oxido-2-(o-tolyl)-4,6-dihydro-2H-thieno[3,4-c]pyrazol-3-yl)acetamide, N-[2-(4-Fluorophenyl)-5-oxo-4,6-dihydrothieno[3,4-c]pyrazol-3-yl]-2-(3-methylphenyl)acetamide. Compounds that share a formula are isomers. They contain the same atoms arranged differently, so their properties, uses and prices can be very different.
What is the degree of unsaturation of C20H18FN3O2S?
C20H18FN3O2S has a degree of unsaturation of 13. That is the total number of rings and pi bonds (a double bond counts as one, a triple bond as two) in any structure with this formula.