Molecular formula
C18H21N3O4S
242 compounds have this formula on CompoundList.
- Molar mass
- 375.44g/mol
- Monoisotopic mass
- 378.1441Da
- Atoms
- 47
- Elements
- 5
- Rings plus double bonds
- 10
The formula C18H21N3O4S describes a molecule made of 18 carbon atoms, 21 hydrogen atoms, 3 nitrogen atoms, 4 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 × 1857.58%12.011 × 18 = 216.198 g/mol
- H Hydrogen × 215.64%1.008 × 21 = 21.168 g/mol
- N Nitrogen × 311.19%14.007 × 3 = 42.021 g/mol
- O Oxygen × 417.05%15.999 × 4 = 63.996 g/mol
- S Sulfur × 18.54%32.06 × 1 = 32.060 g/mol
Look up another formula
Compounds with the formula C18H21N3O4S
Isomers we list, best known first. Open one to see its structure, properties, safety data and suppliers.
Showing 101 to 200 of 242 compounds
![1-[(4-Methylphenyl)sulfonyl]-4-(4-nitrobenzyl)piperazine chemical structure, C18H21N3O4S, CAS 524676-17-3](/s/NTYQPGPLZUDXJC-UHFFFAOYSA-N.svg)
1-[(4-Methylphenyl)sulfonyl]-4-(4-nitrobenzyl)piperazine
CAS 524676-17-3C18H21N3O4S
![1-[(3-Methylphenyl)methyl]-4-(2-nitrophenyl)sulfonylpiperazine chemical structure, C18H21N3O4S, CAS 428504-91-0](/s/VFQVYFSAUIXSAF-UHFFFAOYSA-N.svg)
1-[(3-Methylphenyl)methyl]-4-(2-nitrophenyl)sulfonylpiperazine
CAS 428504-91-0C18H21N3O4S
![1-[(2-Methylphenyl)methyl]-4-(2-nitrophenyl)sulfonylpiperazine chemical structure, C18H21N3O4S, CAS 428852-88-4](/s/MVXGLLXPGVVVAM-UHFFFAOYSA-N.svg)
1-[(2-Methylphenyl)methyl]-4-(2-nitrophenyl)sulfonylpiperazine
CAS 428852-88-4C18H21N3O4S
N-Benzyl-3-nitro-4-piperidin-1-ylbenzenesulfonamide
CAS 324035-95-2C18H21N3O4S
Ethyl 6-methyl-2-oxo-4-((2-oxo-2-(phenethylamino)ethyl)thio)-1,2-dihydropyrimidine-5-carboxylate
CAS 899957-26-7C18H21N3O4S
N1-(2-ethylphenyl)-N2-(4-sulfamoylphenethyl)oxalamide
CAS 899749-00-9C18H21N3O4S
![2-((1-(2-Hydroxyethyl)-2-oxo-2,5,6,7-tetrahydro-1H-cyclopenta[d]pyrimidin-4-yl)thio)-N-(3-methoxyphenyl)acetamide chemical structure, C18H21N3O4S, CAS 942013-18-5](/s/HXHATPVVXSTQFF-UHFFFAOYSA-N.svg)
2-((1-(2-Hydroxyethyl)-2-oxo-2,5,6,7-tetrahydro-1H-cyclopenta[d]pyrimidin-4-yl)thio)-N-(3-methoxyphenyl)acetamide
CAS 942013-18-5C18H21N3O4S
![N1-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-N2-(2-(dimethylamino)-2-(thiophen-2-yl)ethyl)oxalamide chemical structure, C18H21N3O4S, CAS 941932-39-4](/s/MPMFKKNQCNXVKA-UHFFFAOYSA-N.svg)
N1-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-N2-(2-(dimethylamino)-2-(thiophen-2-yl)ethyl)oxalamide
CAS 941932-39-4C18H21N3O4S
N1-(2-(furan-2-yl)-4-(phenylsulfonyl)oxazol-5-yl)-N3,N3-dimethylpropane-1,3-diamine
CAS 862793-16-6C18H21N3O4S
(1-(1,1-Dioxidotetrahydrothiophen-3-yl)-5-phenyl-1H-pyrazol-3-yl)(morpholino)methanone
CAS 942678-47-9C18H21N3O4S
![3-[{[4-(Acetylamino)phenyl]sulfonyl}(benzyl)amino]propanamide chemical structure, C18H21N3O4S, CAS 1010197-04-2](/s/LOEURCLZIMEUFU-UHFFFAOYSA-N.svg)
3-[{[4-(Acetylamino)phenyl]sulfonyl}(benzyl)amino]propanamide
CAS 1010197-04-2C18H21N3O4S
![4-(Dimethylsulfamoyl)-N-{4-[(methylcarbamoyl)methyl]phenyl}benzamide chemical structure, C18H21N3O4S, CAS 1060286-32-9](/s/KMBZBZWMBZLVIQ-UHFFFAOYSA-N.svg)
4-(Dimethylsulfamoyl)-N-{4-[(methylcarbamoyl)methyl]phenyl}benzamide
CAS 1060286-32-9C18H21N3O4S
1-(3-Methoxyphenyl)-3-(1-(methylsulfonyl)-1,2,3,4-tetrahydroquinolin-7-yl)urea
CAS 1203334-42-2C18H21N3O4S
1-(3-(1,1-Dioxidoisothiazolidin-2-yl)phenyl)-3-(2-ethoxyphenyl)urea
CAS 1203198-76-8C18H21N3O4S
1-Benzyl-3-(5-(1,1-dioxidoisothiazolidin-2-yl)-2-methoxyphenyl)urea
CAS 1203011-01-1C18H21N3O4S
![2-(Methanesulfonyl)-N-{[6-(morpholin-4-yl)pyridin-3-yl]methyl}benzamide chemical structure, C18H21N3O4S, CAS 1209616-88-5](/s/MWXBDLUIJCVNCI-UHFFFAOYSA-N.svg)
2-(Methanesulfonyl)-N-{[6-(morpholin-4-yl)pyridin-3-yl]methyl}benzamide
CAS 1209616-88-5C18H21N3O4S
Methyl 3-(2-(cyclohexylamino)-2-oxoethyl)-4-oxo-2-thioxo-1,2,3,4-tetrahydroquinazoline-7-carboxylate
CAS 946215-97-0C18H21N3O4S
Methyl 3-(3-(cyclopentylamino)-3-oxopropyl)-4-oxo-2-thioxo-1,2,3,4-tetrahydroquinazoline-7-carboxylate
CAS 946354-17-2C18H21N3O4S
![[2-[(1-Cyanocyclopentyl)amino]-2-oxoethyl] 5-(cyclopropanecarbonylamino)-3-methylthiophene-2-carboxylate chemical structure, C18H21N3O4S, CAS 1197733-16-6](/s/DGOBEKIBAHBTTK-UHFFFAOYSA-N.svg)
[2-[(1-Cyanocyclopentyl)amino]-2-oxoethyl] 5-(cyclopropanecarbonylamino)-3-methylthiophene-2-carboxylate
CAS 1197733-16-6C18H21N3O4S
N-(2-Methoxy-5-nitrophenyl)-3-(2-thiophen-3-ylpyrrolidin-1-yl)propanamide
CAS 1210183-89-3C18H21N3O4S
![N-(Furan-2-ylmethyl)-2-[3-(3-methylbutyl)-2,4-dioxo-3,4-dihydrothieno[3,2-d]pyrimidin-1(2H)-yl]acetamide chemical structure, C18H21N3O4S, CAS 1252915-22-2](/s/VJEUROWYFUDXJK-UHFFFAOYSA-N.svg)
N-(Furan-2-ylmethyl)-2-[3-(3-methylbutyl)-2,4-dioxo-3,4-dihydrothieno[3,2-d]pyrimidin-1(2H)-yl]acetamide
CAS 1252915-22-2C18H21N3O4S
![N-(2-Methylphenyl)-2-[2-oxo-3-(pyrrolidine-1-sulfonyl)-1,2-dihydropyridin-1-yl]acetamide chemical structure, C18H21N3O4S, CAS 1251608-52-2](/s/KPTAKEZUUXRVKA-UHFFFAOYSA-N.svg)
N-(2-Methylphenyl)-2-[2-oxo-3-(pyrrolidine-1-sulfonyl)-1,2-dihydropyridin-1-yl]acetamide
CAS 1251608-52-2C18H21N3O4S
![N-(3-Methylphenyl)-2-[2-oxo-3-(pyrrolidine-1-sulfonyl)-1,2-dihydropyridin-1-yl]acetamide chemical structure, C18H21N3O4S, CAS 1251627-85-6](/s/AMXLPJKYBRGGMA-UHFFFAOYSA-N.svg)
N-(3-Methylphenyl)-2-[2-oxo-3-(pyrrolidine-1-sulfonyl)-1,2-dihydropyridin-1-yl]acetamide
CAS 1251627-85-6C18H21N3O4S
N-Benzyl-2-(2-oxo-3-(pyrrolidin-1-ylsulfonyl)pyridin-1(2H)-yl)acetamide
CAS 1251704-42-3C18H21N3O4S
- Ethyl 1-(2-(6-oxo-4-(thiophen-2-yl)pyrimidin-1(6H)-yl)acetyl)piperidine-3-carboxylate1251578-39-8C18H21N3O4S
- (E)-N-((1-(3-(Furan-2-yl)acryloyl)piperidin-4-yl)methyl)pyridine-3-sulfonamide1235691-02-7C18H21N3O4S
- N-(1-(Ethylsulfonyl)-1,2,3,4-tetrahydroquinolin-6-yl)-1-methyl-2-oxo-1,2-dihydropyridine-3-carboxamide1324207-17-1C18H21N3O4S
- 6-(3,4-Dimethoxyphenyl)-2-[2-oxo-2-(thiomorpholin-4-yl)ethyl]pyridazin-3(2H)-one1232776-32-7C18H21N3O4S
- 2-(2,3-Dihydro-1-benzofuran-6-yl)-N-[1-(1,1-dioxidotetrahydrothiophen-3-yl)-3-methyl-1H-pyrazol-5-yl]acetamide1401589-98-7C18H21N3O4S
- N-(5-(2,5-Dimethylfuran-3-carbonyl)-4,5,6,7-tetrahydrothiazolo[5,4-c]pyridin-2-yl)tetrahydrofuran-2-carboxamide1396850-95-5C18H21N3O4S
- N-{2-[4-(Furan-2-yl)-1-methyl-1H-imidazol-2-yl]ethyl}-4-methoxy-2-methylbenzene-1-sulfonamide1421459-13-3C18H21N3O4S
- N-(2-(Benzo[b]thiophen-2-yl)-2-hydroxypropyl)-4-ethyl-2,3-dioxopiperazine-1-carboxamide2034472-62-1C18H21N3O4S
- 1-(3-((6-Methylpyridazin-3-yl)oxy)pyrrolidin-1-yl)-3-(phenylsulfonyl)propan-1-one2034482-19-2C18H21N3O4S
- 2-(Cyclopentyloxy)-N-(3-methanesulfonamidophenyl)pyridine-4-carboxamide2034298-92-3C18H21N3O4S
- (1,1-Dioxidotetrahydrothiophen-3-yl)(3-(3-methyl-1,2,4-oxadiazol-5-yl)-4-phenylpyrrolidin-1-yl)methanone1903434-60-5C18H21N3O4S
- 4-((1-((2,3-Dihydrobenzofuran-5-yl)sulfonyl)piperidin-4-yl)oxy)-2-methylpyrimidine2097888-11-2C18H21N3O4S
- 1-(2,5-Diethoxy-4-methylbenzenesulfonyl)-5-methyl-1H-1,2,3-benzotriazole2419700-69-7C18H21N3O4S
- 1-(2-Methyl-4-nitrophenyl)-4-(4-methylphenyl)sulfonylpiperazine709005-82-3C18H21N3O4S
- N-(4-(5-(Furan-2-yl)-1-isobutyryl-4,5-dihydro-1H-pyrazol-3-yl)phenyl)methanesulfonamide851717-81-2C18H21N3O4S
- Methyl 6-amino-5-cyano-2-methyl-4-[4-(morpholin-4-ylmethyl)thiophen-2-yl]-4H-pyran-3-carboxylate727663-31-2C18H21N3O4S
- 3,4-Dimethoxy-N-[2-(7-methylimidazo[1,2-a]pyridin-2-yl)ethyl]benzenesulfonamide868978-96-5C18H21N3O4S
- N-(3,5-Dimethoxyphenyl)-2-[(2-oxo-5,6,7,8-tetrahydro-1H-quinazolin-4-yl)sulfanyl]acetamide946324-29-4C18H21N3O4S
- N-(3,4-Dimethoxyphenyl)-2-[(2-oxo-5,6,7,8-tetrahydro-1H-quinazolin-4-yl)sulfanyl]acetamide1001519-94-3C18H21N3O4S
- N-(2,4-Dimethoxyphenyl)-2-[(2-oxo-5,6,7,8-tetrahydro-1H-quinazolin-4-yl)sulfanyl]acetamide946269-69-8C18H21N3O4S
- N-(2,5-Dimethoxyphenyl)-2-[(2-oxo-5,6,7,8-tetrahydro-1H-quinazolin-4-yl)sulfanyl]acetamide946372-27-6C18H21N3O4S
- Ethyl 4-[2-(3,5-dimethylanilino)-2-oxoethyl]sulfanyl-6-methyl-2-oxo-1H-pyrimidine-5-carboxylate946252-95-5C18H21N3O4S
- Ethyl 4-[2-(2,5-dimethylanilino)-2-oxoethyl]sulfanyl-6-methyl-2-oxo-1H-pyrimidine-5-carboxylate946332-45-2C18H21N3O4S
- Ethyl 4-[2-(2,4-dimethylanilino)-2-oxoethyl]sulfanyl-6-methyl-2-oxo-1H-pyrimidine-5-carboxylate946209-53-6C18H21N3O4S
- Ethyl 6-methyl-4-[2-[(4-methylphenyl)methylamino]-2-oxoethyl]sulfanyl-2-oxo-1H-pyrimidine-5-carboxylate900002-71-3C18H21N3O4S
- (5,6-Dihydro-1,4-dioxin-2-yl)(4-(6-ethoxybenzo[d]thiazol-2-yl)piperazin-1-yl)methanone897470-28-9C18H21N3O4S
- N1-(4-ethylphenyl)-N2-(4-sulfamoylphenethyl)oxalamide887204-54-8C18H21N3O4S
- N1-(2,6-dimethylphenyl)-N2-(4-sulfamoylphenethyl)oxalamide887204-61-7C18H21N3O4S
- Methyl (2-(4-(dimethylamino)benzamido)-4,5-dimethylthiophene-3-carbonyl)carbamate896308-86-4C18H21N3O4S
- (5,6-Dihydro-1,4-dioxin-2-yl)(4-(4-ethoxybenzo[d]thiazol-2-yl)piperazin-1-yl)methanone897478-86-3C18H21N3O4S
- N-Benzyl-2-(2-oxo-5-pyrrolidin-1-ylsulfonylpyridin-1-yl)acetamide1251625-95-2C18H21N3O4S
- N-((1-(4-Ethoxyphenyl)-5-oxopyrrolidin-3-yl)methyl)pyridine-3-sulfonamide954605-18-6C18H21N3O4S
- N1-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-N2-(2-(dimethylamino)-2-(thiophen-3-yl)ethyl)oxalamide946199-88-8C18H21N3O4S
- 4-(Pyrrolidin-1-ylsulfonyl)-N-(4,5,6,7-tetrahydrobenzo[c]isoxazol-3-yl)benzamide946370-44-1C18H21N3O4S
- 4-(N-Cyclopropyl-N-methylsulfamoyl)-N-(4,5,6,7-tetrahydrobenzo[c]isoxazol-3-yl)benzamide946224-81-3C18H21N3O4S
- 1-((4-Methoxyphenyl)sulfonyl)-N-(pyridin-3-yl)piperidine-3-carboxamide919745-78-1C18H21N3O4S
- 2-((1-(2-(2,6-Dimethylmorpholino)-2-oxoethyl)-1H-indol-3-yl)sulfonyl)acetonitrile894023-62-2C18H21N3O4S
- Methyl 4-(((1-(2-(cyclopropylamino)-2-oxoethyl)-5-(hydroxymethyl)-1H-imidazol-2-yl)thio)methyl)benzoate921867-76-7C18H21N3O4S
- 1-(3-Hydroxypropyl)-4-((3-nitrobenzyl)thio)-5,6,7,8-tetrahydroquinazolin-2(1H)-one899974-09-5C18H21N3O4S
- 5-Cyclopropyl-1-(1,1-dioxidotetrahydrothiophen-3-yl)-N-(3-methoxyphenyl)-1H-pyrazole-3-carboxamide942812-75-1C18H21N3O4S
- 5-Cyclopropyl-1-(1,1-dioxidotetrahydrothiophen-3-yl)-N-(4-methoxyphenyl)-1H-pyrazole-3-carboxamide942727-51-7C18H21N3O4S
- Butyl 4-[2-(2-acetamido-1,3-thiazol-4-yl)acetamido]benzoate921522-34-1C18H21N3O4S
- 1-(5-(1,1-Dioxidoisothiazolidin-2-yl)-2-methoxyphenyl)-3-(m-tolyl)urea1202982-91-9C18H21N3O4S
- 1-(3-Nitrophenyl)ethyl 3-[4,6-dimethyl-2-(methylsulfanyl)pyrimidin-5-yl]propanoate1110821-03-8C18H21N3O4S
- 1-(3,4-Dimethoxybenzoyl)-N-(thiazol-2-yl)piperidine-4-carboxamide1207012-16-5C18H21N3O4S
- Methyl (1-{[6-oxo-3-(thiophen-2-yl)pyridazin-1(6H)-yl]acetyl}piperidin-4-yl)acetate1282099-39-1C18H21N3O4S
- Rabeprazole sulfone-d31330261-33-0C18H21N3O4S
- N-(4-(Dimethylamino)phenethyl)-3-methyl-2-oxo-2,3-dihydrobenzo[d]oxazole-5-sulfonamide1448047-10-6C18H21N3O4S
- (E)-3-(Furan-3-yl)-N-((1-(pyridin-3-ylsulfonyl)piperidin-4-yl)methyl)acrylamide1798397-52-0C18H21N3O4S
- N-(4-(2-(4-(2,4-Dioxothiazolidin-3-yl)piperidin-1-yl)-2-oxoethyl)phenyl)acetamide1795088-14-0C18H21N3O4S
- 1'-[(1,3,5-Trimethyl-1H-pyrazol-4-yl)sulfonyl]-3H-spiro[2-benzofuran-1,4'-piperidine]-3-one1705882-34-3C18H21N3O4S
- 1'-[(1,3,5-Trimethyl-1H-pyrazol-4-yl)sulfonyl]-3H-spiro[2-benzofuran-1,3'-piperidine]-3-one1705316-23-9C18H21N3O4S
- N-[(1r,4r)-4-(Pyrimidin-2-yloxy)cyclohexyl]-2,3-dihydro-1-benzofuran-5-sulfonamide2034248-90-1C18H21N3O4S
- N-(4-((4-(Pyridin-4-yloxy)piperidin-1-yl)sulfonyl)phenyl)acetamide2034471-19-5C18H21N3O4S
- 1-(Benzo[d][1,3]dioxol-5-yl)-3-(2-(furan-3-yl)-2-thiomorpholinoethyl)urea2034398-42-8C18H21N3O4S
- 1-(Benzo[d][1,3]dioxol-5-yl)-3-(2-(furan-2-yl)-2-thiomorpholinoethyl)urea2034399-63-6C18H21N3O4S
- N-(3-Methyl-4-((3-(pyridin-3-yloxy)azetidin-1-yl)sulfonyl)phenyl)propionamide1904048-47-0C18H21N3O4S
- N,N-Dimethyl-4-(3-(pyridin-4-yloxy)pyrrolidine-1-carbonyl)benzenesulfonamide2034494-71-6C18H21N3O4S
- N-(2-(3-Methyl-2,2-dioxidobenzo[c][1,2,5]thiadiazol-1(3H)-yl)ethyl)-2-(o-tolyloxy)acetamide2034488-25-8C18H21N3O4S
- 2-(Benzyloxy)-N-(2-(3-methyl-2,2-dioxidobenzo[c][1,2,5]thiadiazol-1(3H)-yl)ethyl)acetamide2034453-12-6C18H21N3O4S
- 6-(4-(Benzylsulfonyl)piperidine-1-carbonyl)-2-methylpyridazin-3(2H)-one2034467-22-4C18H21N3O4S
- 2-(1,1-Dioxidotetrahydrothiophen-3-yl)-N-(2-methoxyphenyl)-2,4,5,6-tetrahydrocyclopenta[c]pyrazole-3-carboxamide2319809-05-5C18H21N3O4S
- 2-(1,1-Dioxidotetrahydrothiophen-3-yl)-N-(3-methoxyphenyl)-2,4,5,6-tetrahydrocyclopenta[c]pyrazole-3-carboxamide2309312-96-5C18H21N3O4S
- N-(2-(3-Oxo-5,6,7,8-tetrahydrocinnolin-2(3H)-yl)ethyl)-2,3-dihydrobenzofuran-5-sulfonamide2034366-24-8C18H21N3O4S
- N-(2-(3-Cyclopropyl-6-oxopyridazin-1(6H)-yl)ethyl)-3-(phenylsulfonyl)propanamide2034534-07-9C18H21N3O4S
- 2-((1H-Indol-3-yl)thio)-N-(2-(2-(2,5-dioxopyrrolidin-1-yl)ethoxy)ethyl)acetamide2034204-08-3C18H21N3O4S
- 2-[4-(Furan-2-yl)phenyl]-2-hydroxy-S-(1,3,5-trimethyl-1H-pyrazol-4-yl)ethane-1-sulfonamido2097922-56-8C18H21N3O4S
- 3-{[1-(2,3-Dihydro-1-benzofuran-5-sulfonyl)piperidin-4-yl]methyl}-3,4-dihydropyrimidin-4-one2194843-52-0C18H21N3O4S
- Methyl 4-{[3-(1H-imidazol-1-yl)-8-azabicyclo[3.2.1]octan-8-yl]sulfonyl}benzoate2320473-78-5C18H21N3O4S
- 4-[4-(3,4-Dimethoxyphenyl)-1,3-thiazol-2-yl]-5-imino-1-(2-methoxyethyl)-2,5-dihydro-1H-pyrrol-3-ol929858-93-5C18H21N3O4S
- 4-(4-Nitrobenzene-1-sulfonyl)-N-[(piperidin-1-yl)methyl]aniline60515-99-3C18H21N3O4S
- 4-(Benzenesulfonyl)-N-(4-methoxyphenyl)piperazine-1-carboxamide903219-36-3C18H21N3O4S
- 4-Methoxy-N-(pyridin-3-ylmethyl)-3-(pyrrolidine-1-carbonyl)benzenesulfonamide879048-36-9C18H21N3O4S
- 4-Methoxy-N-(pyridin-4-ylmethyl)-3-(pyrrolidine-1-carbonyl)benzenesulfonamide892683-63-5C18H21N3O4S
- Ethyl 4-[2-(4-ethylanilino)-2-oxoethyl]sulfanyl-6-methyl-2-oxo-1H-pyrimidine-5-carboxylate900002-11-1C18H21N3O4S
- 4-{[N-(Methylsulfonyl)-N-(2-phenylethyl)glycyl]amino}benzamide769160-60-3C18H21N3O4S
Frequently asked questions
What is the molar mass of C18H21N3O4S?
The molar mass of C18H21N3O4S is 375.44 g/mol, calculated from standard atomic weights for 18 carbon atoms, 21 hydrogen atoms, 3 nitrogen atoms, 4 oxygen atoms and 1 sulfur atom. The monoisotopic mass is 378.1441 Da.
How many compounds have the formula C18H21N3O4S?
CompoundList lists 242 compounds with the molecular formula C18H21N3O4S, including 1-[(4-Methylphenyl)sulfonyl]-4-(4-nitrobenzyl)piperazine, 1-[(3-Methylphenyl)methyl]-4-(2-nitrophenyl)sulfonylpiperazine, 1-[(2-Methylphenyl)methyl]-4-(2-nitrophenyl)sulfonylpiperazine. 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 C18H21N3O4S?
C18H21N3O4S has a degree of unsaturation of 10. 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.