Chembase list of 866358 unique molecular structures

$$$$ Data More

M. F.

C8H18O3

Suppliers	Catalog Number
Sigma Aldrich	T60402 75580
MP Biomedicals	05209863
Alfa Aesar	L06004

Database	Data ID
PubChem	66221

M. W.

162.22672

CAS

78-39-7

Similarity

N/A

ID: 109102

1-ethyl-4-nitrobenzene

$$$$ Data

M. F.

C8H9NO2

Suppliers	Catalog Number
Sigma Aldrich	E41001
MP Biomedicals	05209864

Database	Data ID
PubChem	7480

M. W.

151.16256

CAS

100-12-9

Similarity

N/A

ID: 109103

pentadecan-3-one

$$$$ Data

M. F.

C15H30O

Suppliers	Catalog Number
MP Biomedicals	05209866

Database	Data ID
PubChem	545972

M. W.

226.3981

CAS

Similarity

N/A

ID: 109104

but-2-enediamide

$$$$ Data

M. F.

C4H6N2O2

Suppliers	Catalog Number
MP Biomedicals	05209870
Alfa Aesar	B25200

Database	Data ID
PubChem	446408

M. W.

114.10264

CAS

627-64-5

Similarity

N/A

ID: 109105

but-2-enedioyl dichloride

$$$$ Data

M. F.

C4H2Cl2O2

Suppliers	Catalog Number
Sigma Aldrich	151386 47960
MP Biomedicals	05209871
Alfa Aesar	A14540

Database	Data ID
PubChem	5325504

M. W.

152.96348

CAS

627-63-4

Similarity

N/A

ID: 109106

decane-1,10-diol

$$$$ Data More

M. F.

C10H22O2

Suppliers	Catalog Number
Sigma Aldrich	D1203 30580
MP Biomedicals	05209877
Alfa Aesar	A13923

Database	Data ID
PubChem	37153

M. W.

174.28048

CAS

112-47-0

Similarity

N/A

ID: 109107

CAS_150-38-9(anhydrous) molecular structure

trisodium 2-({2-[bis(carboxylatomethyl)amino]ethyl}(carboxymethyl)amino)acetate ...

$$$$ Data

M. F.

C10H17N2Na3O10

Suppliers	Catalog Number
Sigma Aldrich	03710
MP Biomedicals	05209880

Database	Data ID
PubChem	25021605

M. W.

394.21869

CAS

150-38-9(anhydrous)

Similarity

N/A

ID: 109108

ethyl 2-fluoroacetate

$$$$ Data

M. F.

C4H7FO2

Suppliers	Catalog Number
Sigma Aldrich	163813 46990
MP Biomedicals	05209881
Chemik	CHO0150

Database	Data ID
PubChem	9988

M. W.

106.0955832

CAS

459-72-3

Similarity

N/A

ID: 109109

2-ethylhexanal

$$$$ Data More

M. F.

C8H16O

Suppliers	Catalog Number
Sigma Aldrich	E29109 03290
MP Biomedicals	05209882
Alfa Aesar	B23471

Database	Data ID
PubChem	31241

M. W.

128.21204

CAS

123-05-7

Similarity

N/A

ID: 109110

5-ethoxy-5-oxopentanoic acid

$$$$ Data

M. F.

C7H12O4

Suppliers	Catalog Number
MP Biomedicals	05209885
Alfa Aesar	L03941

Database	Data ID
PubChem	66114

M. W.

160.16778

CAS

1070-62-8

Similarity

N/A

ID: 109111

2-ethylhexyl octyl phenyl phosphite

$$$$ Data

M. F.

C22H39O3P

Suppliers	Catalog Number
MP Biomedicals	05209888

Database	Data ID
PubChem	110970

M. W.

382.517021

CAS

7346-61-4

Similarity

N/A

ID: 109112

cyclohexyl prop-2-enoate

$$$$ Data

M. F.

C9H14O2

Suppliers	Catalog Number
MP Biomedicals	05209890
Alfa Aesar	L12925

Database	Data ID
PubChem	18298

M. W.

154.20626

CAS

3066-71-5

Similarity

N/A

ID: 109113

ethyl dodecanoate

$$$$ Data

M. F.

C14H28O2

Suppliers	Catalog Number
Sigma Aldrich	L4625 W244104 W244112 (more...)
MP Biomedicals	05209893
Alfa Aesar	A11188

Database	Data ID
PubChem	7800

M. W.

228.37092

CAS

106-33-2

Similarity

N/A

ID: 109114

cyclopropyl(4-ethylphenyl)methanone

$$$$ Data

M. F.

C12H14O

Suppliers	Catalog Number
MP Biomedicals	05209898

Database	Data ID
PubChem	96399

M. W.

174.23896

CAS

50664-71-6

Similarity

N/A

ID: 109115

2-methylprop-2-enamide

$$$$ Data More

M. F.

C4H7NO

Suppliers	Catalog Number
Sigma Aldrich	109606 64090
MP Biomedicals	05209904
Alfa Aesar	L15013

Database	Data ID
Wikipedia	Methacrylamide
PubChem	6595

M. W.

85.10448

CAS

79-39-0

Similarity

N/A

ID: 109116

chromium(3+) ion 2-methylprop-2-enoic acid trichloride

$$$$ Data

M. F.

C4H6Cl3CrO2

Suppliers	Catalog Number
MP Biomedicals	05209905

Database	Data ID
PubChem	18008698

M. W.

244.44434

CAS

Similarity

N/A

ID: 109117

1,6-bis(propan-2-yl) hexanedioate

$$$$ Data

M. F.

C12H22O4

Suppliers	Catalog Number
MP Biomedicals	05209912

Database	Data ID
PubChem	23368

M. W.

230.30068

CAS

6938-94-9

Similarity

N/A

ID: 109118

2-(2-aminoethoxy)ethan-1-ol

$$$$ Data More

M. F.

C4H11NO2

Suppliers	Catalog Number
Sigma Aldrich	A54059
MP Biomedicals	05209913
Alfa Aesar	L18897

Database	Data ID
PubChem	13578

M. W.

105.13564

CAS

929-06-6

Similarity

N/A

ID: 109119

3,7-dimethyloct-1-en-2-ol

$$$$ Data

M. F.

C10H20O

Suppliers	Catalog Number
MP Biomedicals	05209915

Database	Data ID
PubChem	162479

M. W.

156.2652

CAS

41678-36-8

Similarity

N/A

ID: 109120

4-methoxypyridin-1-ium-1-olate hydrate

$$$$ Data

M. F.

C6H9NO3

Suppliers	Catalog Number
Sigma Aldrich	349461
MP Biomedicals	05209918
TRC	M267130

Database	Data ID
PubChem	16212293

M. W.

143.14056

CAS

1122-96-9

Similarity

N/A

ID: 109121

2-methylprop-2-en-1-yl 2-methylprop-2-enoate

$$$$ Data

M. F.

C8H12O2

Suppliers	Catalog Number
MP Biomedicals	05209920

Database	Data ID
PubChem	229993

M. W.

140.17968

CAS

816-74-0

Similarity

N/A

ID: 109122

N-acetyl-N-(9H-fluoren-2-yl)acetamide

$$$$ Data

M. F.

C17H15NO2

Suppliers	Catalog Number
MP Biomedicals	05209928

Database	Data ID
PubChem	12553

M. W.

265.3065

CAS

642-65-9

Similarity

N/A

ID: 109123

bis(prop-2-en-1-yl)amine

$$$$ Data

M. F.

C6H11N

Suppliers	Catalog Number
Sigma Aldrich	D9603
MP Biomedicals	05209929
Alfa Aesar	A18950

Database	Data ID
PubChem	31279

M. W.

97.15824

CAS

124-02-7

Similarity

N/A

ID: 109124

copper(2+) ion dirubidium(1+) ion disulfate

$$$$ Data

M. F.

CuO8Rb2S2

Suppliers	Catalog Number
MP Biomedicals	05209932

Database	Data ID
PubChem	25021454

M. W.

426.6068

CAS

Similarity

N/A

ID: 109125

tricopper(2+) ion bis(2-hydroxypropane-1,2,3-tricarboxylate)

$$$$ Data

M. F.

C12H10Cu3O14

Suppliers	Catalog Number
MP Biomedicals	05209933

Database	Data ID
PubChem	6451521

M. W.

568.8374

CAS

866-82-0

Similarity

N/A

ID: 109126

copper(2+) ion 2,3-dihydroxybutanedioate

$$$$ Data

M. F.

C4H4CuO6

Suppliers	Catalog Number
MP Biomedicals	05209934

Database	Data ID
PubChem	2734041

M. W.

211.61696

CAS

27004-40-6

Similarity

N/A

ID: 109127

oxo[(oxochromio)oxy]chromium; bis(oxocopper)

$$$$ Data

M. F.

Cr2Cu2O5

Suppliers	Catalog Number
MP Biomedicals	05209937

Database	Data ID
Wikipedia	Copper_chromite
PubChem	3084101

M. W.

311.0812

CAS

12053-18-8

Similarity

N/A

ID: 109128

(3aR,4S,9aS)-4-(3,4-dihydroxyphenyl)-6,7-dihydroxy-1H,3H,3aH,4H,9H,9aH-naphtho[2...

$$$$ Data

M. F.

C18H16O6

Suppliers	Catalog Number
MP Biomedicals	05209942

Database	Data ID
PubChem	475935

M. W.

328.31604

CAS

Similarity

N/A

ID: 109129

copper(2+) ion selandiide

$$$$ Data

M. F.

CuSe

Suppliers	Catalog Number
MP Biomedicals	05209943

Database	Data ID
PubChem	73980

M. W.

142.506

CAS

1317-41-5

Similarity

N/A

ID: 109130

copper(2+) ion sodium trichloride

$$$$ Data

M. F.

Cl3CuNa

Suppliers	Catalog Number
MP Biomedicals	05209944

Database	Data ID
PubChem	25021470

M. W.

192.89477

CAS

Similarity

N/A

ID: 109131

$l^{1}-copper(1+) ion potassium bis(iminomethanide)

$$$$ Data

M. F.

C2CuKN2

Suppliers	Catalog Number
MP Biomedicals	05209946

Database	Data ID
PubChem	16058202

M. W.

154.6791

CAS

13682-73-0

Similarity

N/A

ID: 109132

(cyclodecylideneamino)urea

$$$$ Data

M. F.

C11H21N3O

Suppliers	Catalog Number
MP Biomedicals	05209950

Database	Data ID
PubChem	585832

M. W.

211.30394

CAS

Similarity

N/A

ID: 109133

2-{2-[1,4a-dimethyl-7-(propan-2-yl)-1,2,3,4,4a,4b,5,6,10,10a-decahydrophenanthre...

$$$$ Data

M. F.

C44H66O5

Suppliers	Catalog Number
MP Biomedicals	05209951

Database	Data ID
PubChem	44135823

M. W.

674.99184

CAS

Similarity

N/A

ID: 109134

1,4-diethylbenzene

$$$$ Data More

M. F.

C10H14

Suppliers	Catalog Number
Sigma Aldrich	D91004 32020 32018
MP Biomedicals	05209954
Alfa Aesar	A13343

Database	Data ID
PubChem	7734

M. W.

134.21816

CAS

105-05-5

Similarity

N/A

ID: 109135

{[amino(phenoxy)phosphoryl]oxy}benzene

$$$$ Data

M. F.

C12H12NO3P

Suppliers	Catalog Number
Sigma Aldrich	367915
MP Biomedicals	05209955
Alfa Aesar	L07155

Database	Data ID
PubChem	74836

M. W.

249.202341

CAS

2015-56-7

Similarity

N/A

ID: 109136

iodyl iodate

$$$$ Data

M. F.

I2O5

Suppliers	Catalog Number
Sigma Aldrich	278890 229709
MP Biomedicals	05209960
Alfa Aesar	87682

Database	Data ID
Wikipedia	Iodine_pentoxide
PubChem	159402

M. W.

333.80594

CAS

12029-98-0

Similarity

N/A

ID: 109137

3-(4-iodophenyl)prop-2-enoic acid

$$$$ Data

M. F.

C9H7IO2

Suppliers	Catalog Number
MP Biomedicals	05209963

Database	Data ID
PubChem	5871757

M. W.

274.05515

CAS

Similarity

N/A

ID: 109138

(4-aminopentyl)diethylamine

$$$$ Data More

M. F.

C9H22N2

Suppliers	Catalog Number
Sigma Aldrich	A48806
MP Biomedicals	05209964
Bide Pharmatech	BD7144

Database	Data ID
PubChem	78953

M. W.

158.28438

CAS

140-80-7

Similarity

N/A

ID: 109139

1-[2,2-dichloro-1-(4-ethylphenyl)ethyl]-4-ethylbenzene

$$$$ Data

M. F.

C18H20Cl2

Suppliers	Catalog Number
Sigma Aldrich	45615 PS73
MP Biomedicals	05209967

Database	Data ID
PubChem	6295

M. W.

307.2574

CAS

72-56-0

Similarity

N/A

ID: 109140

1,5-dibromopentane

$$$$ Data More

M. F.

C5H10Br2

Suppliers	Catalog Number
Sigma Aldrich	128007 34260
MP Biomedicals	05209971
Alfa Aesar	A18465

Database	Data ID
PubChem	8100

M. W.

229.9409

CAS

111-24-0

Similarity

N/A

ID: 109141

2,2-dichloro-3,3-dimethylbutane

$$$$ Data

M. F.

C6H12Cl2

Suppliers	Catalog Number
MP Biomedicals	05209973

Database	Data ID
PubChem	241493

M. W.

155.06548

CAS

594-84-3

Similarity

N/A

ID: 109142

2-aminophenol; sulfuric acid

$$$$ Data

M. F.

C6H9NO5S

Suppliers	Catalog Number
MP Biomedicals	05209979

Database	Data ID
PubChem	12196936

M. W.

207.20436

CAS

Similarity

N/A

ID: 109143

4-(2,4,5-triethoxyphenyl)benzene-1-diazonium hydrogen oxalate

$$$$ Data

M. F.

C20H22N2O7

Suppliers	Catalog Number
MP Biomedicals	05209983

Database	Data ID
PubChem	110137

M. W.

402.39788

CAS

68399-86-0

Similarity

N/A

ID: 109144

1,2-dibromocyclohexane

$$$$ Data

M. F.

C6H10Br2

Suppliers	Catalog Number
MP Biomedicals	05209989
Bide Pharmatech	BD53179

Database	Data ID
PubChem	95314

M. W.

241.9516

CAS

5401-62-7

Similarity

N/A

ID: 109145

2,3,4,5,6-pentahydroxyhexanamide

$$$$ Data

M. F.

C6H13NO6

Suppliers	Catalog Number
MP Biomedicals	05209998

Database	Data ID
PubChem	219903

M. W.

195.17052

CAS

7256-14-6

Similarity

N/A

ID: 109146

3-ethyl-2-[3-(3-ethyl-2,3-dihydro-1,3-benzoselenazol-2-ylidene)-2-methylprop-1-e...

$$$$ Data

M. F.

C22H23IN2Se2

Suppliers	Catalog Number
MP Biomedicals	05210001

Database	Data ID
PubChem	6507075

M. W.

600.25589

CAS

7310-87-4

Similarity

N/A

ID: 109147

(2R,3S)-2-(3,4-dihydroxyphenyl)-3,7-dihydroxy-3,4-dihydro-2H-1-benzopyran-4-one

$$$$ Data

M. F.

C15H12O6

Suppliers	Catalog Number
MP Biomedicals	05210015

Database	Data ID
PubChem	439493

M. W.

288.25218

CAS

20725-03-5

Similarity

N/A

ID: 109148

2-(acetyloxy)ethyl acetate

$$$$ Data

M. F.

C6H10O4

Suppliers	Catalog Number
Sigma Aldrich	239771 525200 31470
MP Biomedicals	05210019

Database	Data ID
PubChem	8121

M. W.

146.1412

CAS

111-55-7

Similarity

N/A

ID: 109149

4-{[4-(acetyloxy)phenyl](pyridin-2-yl)methyl}phenyl acetate

$$$$ Data More

M. F.

C22H19NO4

Suppliers	Catalog Number
Selleck Chemicals	S4047
Sigma Aldrich	B1390
MP Biomedicals	05210023

Database	Data ID
Wikipedia	Bisacodyl
PubChem	2391

M. W.

361.39056

CAS

30652-11-0

Similarity

N/A

ID: 109150

1,3-dihydroxypropan-2-yl tetradecanoate

$$$$ Data

M. F.

C17H34O4

Suppliers	Catalog Number
MP Biomedicals	05210027

Database	Data ID
PubChem	137938

M. W.

302.44946

CAS

27214-38-6

Similarity

N/A

Part I: Carbon
- I.1: Carbon-Carbon Bonds
- I.1.1 Alkanes
- Primary carbon
- Secondary carbon
- Tertiary carbon
- Quaternary carbon
- I.1.2 C-C double and Triple Bonds
- Alkene
- Alkyne
- Allene
- I.2: One Carbon-Hetero Bond
- I.2.1 Alkyl Halogenides
- Alkylchloride
- Alkylfluoride
- Alkylbromide
- Alkyliodide
- I.2.2 Alcohols and Ethers
- Alcohol
- Primary alcohol
- Secondary alcohol
- Tertiary alcohol
- Dialkylether
- Dialkylthioether
- Alkylarylether
- Diarylether
- Alkylarylthioether
- Diarylthioether
- Oxonium
- I.2.3 Amines
- Amine
- Primary aliphatic amine
- Secondary aliphatic amine
- Tertiary aliphatic amine
- Quaternary aliphatic ammonium
- Primary aromatic amine
- Secondary aromatic amine
- Tertiary aromatic amine
- Quaternary aromatic ammonium
- Secondary mixed amine
- Tertiary mixed amine
- Quaternary mixed ammonium
- Ammonium
- I.2.4 Others
- Alkylthiol
- Dialkylthioether
- Alkylarylthioether
- Disulfide
- 1,2-Aminoalcohol
- 1,2-Diol
- 1,1-Diol
- Hydroperoxide
- Peroxo
- Organolithium compounds
- Organomagnesium compounds
- Organometallic compounds
- I.3: Two Carbon-Hetero Bonds (Carbonyl and Derivatives)
- I.3.1 Double Bond to Hetero
- Aldehyde
- Ketone
- Thioaldehyde
- Thioketone
- Imine
- Immonium
- Oxime
- Oximether
- I.3.2. Two Single Bonds to Hetero
- Acetal
- Hemiacetal
- Aminal
- Hemiaminal
- Thioacetal
- Thiohemiacetal
- Halogen acetal like
- Acetal like
- Halogenmethylen ester and similar
- NOS methylen ester and similar
- Hetero methylen ester and similar
- Cyanhydrine
- I.3.3 Single Bond to Hetero, C=C Double Bond (Enols and Similar)
- Chloroalkene
- Fluoroalkene
- Bromoalkene
- Iodoalkene
- Enol
- Endiol
- Enolether
- Enolester
- Enamine
- Thioenol
- Thioenolether
- I.4: Three Carbon-Hetero Bonds (Carboxyl and Derivatives)
- Acylchloride
- Acylfluoride
- Acylbromide
- Acyliodide
- Acylhalide
- Carboxylic acid
- Carboxylic ester
- Lactone
- Carboxylic anhydride
- Carboxylic acid derivative
- Carbothioic acid
- Carbothioic S ester
- Carbothioic S lactone
- Carbothioic O ester
- Carbothioic O lactone
- Carbothioic halide
- Carbodithioic acid
- Carbodithioic ester
- Carbodithiolactone
- Amide
- Primary amide
- Secondary amide
- Tertiary amide
- Lactam
- Alkyl imide
- N hetero imide
- Imide acidic
- Thioamide
- Thiolactam
- Oximester
- Amidine
- Hydroxamic acid
- Hydroxamic acid ester
- Imidoacid
- Imidoacid cyclic
- Imidoester
- Imidolactone
- Imidothioacid
- Imidothioacid cyclic
- Imidothioester
- Imidothiolactone
- Amidine
- Imidolactam
- Imidoylhalide
- Imidoylhalide cyclic
- Amidrazone
- Alpha aminoacid
- Alpha hydroxyacid
- Peptide middle
- Peptide C term
- Peptide N term
- Carboxylic orthoester
- Ketene
- Ketenacetal
- Nitrile
- Isonitrile
- Vinylogous carbonyl or carboxyl derivative
- Vinylogous acid
- Vinylogous ester
- Vinylogous amide
- Vinylogous halide
- I.5: Four Carbon-Hetero Bonds (Carbonic Acid and Derivatives)
- Carbonic acid dieester
- Carbonic acid esterhalide
- Carbonic acid monoester
- Carbonic acid derivatives
- Thiocarbonic acid dieester
- Thiocarbonic acid esterhalide
- Thiocarbonic acid monoester
- Urea
- Thiourea
- Isourea
- Isothiourea
- Guanidine
- Carbaminic acid
- Urethan(Carbamate ester)
- Biuret
- Semicarbazide
- Carbazide
- Semicarbazone
- Carbazone
- Thiosemicarbazide
- Thiocarbazide
- Thiosemicarbazone
- Thiocarbazone
- Isocyanate
- Cyanate
- Isothiocyanate
- Thiocyanate
- Carbodiimide
- Orthocarbonic derivatives
- I.6 Aromatics
- Phenol
- 1,2-Diphenol
- Arylchloride
- Arylfluoride
- Arylbromide
- Aryliodide
- Arylthiol
- Iminoarene
- Oxoarene
- Thioarene
- Hetero N basic H
- Hetero N basic no H
- Hetero N nonbasic
- Hetero O
- Hetero S
- Heteroaromatic
Part II: N, S, P, Si, B
- II.1 Nitrogen
- Nitrite
- Thionitrite
- Nitrate
- Nitro
- Nitroso
- Azide
- Acylazide
- Diazo
- Diazonium
- Nitrosamine
- Nitrosamide
- N-Oxide
- Hydrazine
- Hydrazone
- Hydroxylamine
- II.2 Sulfur
- Sulfon
- Sulfoxide
- Sulfonium
- Sulfuric acid
- Sulfuric monoester
- Sulfuric diester
- Sulfuric monoamide
- Sulfuric diamide
- Sulfuric esteramide
- Sulfuric derivative
- Sulfonic acid
- Sulfonamide
- Sulfonic ester
- Sulfonic halide
- Sulfonic derivative
- Sulfinic acid
- Sulfinic amide
- Sulfinic ester
- Sulfinic halide
- Sulfinic derivative
- Sulfenic acid
- Sulfenic amide
- Sulfenic ester
- Sulfenic halide
- Sulfenic derivative
- II.3 Phosphorous
- Phosphine
- Phosphine oxide
- Phosphonium
- Phosphorylen
- Phosphonic acid
- Phosphonic monoester
- Phosphonic diester
- Phosphonic monoamide
- Phosphonic diamide
- Phosphonic esteramide
- Phosphonic acid derivative
- Phosphoric acid
- Phosphoric monoester
- Phosphoric diester
- Phosphoric triester
- Phosphoric monoamide
- Phosphoric diamide
- Phosphoric triamide
- Phosphoric monoestermonoamide
- Phosphoric diestermonoamide
- Phosphoric monoesterdiamide
- Phosphoric acid derivative
- Phosphinic acid
- Phosphinic ester
- Phosphinic amide
- Phosphinic acid derivative
- Phosphonous acid
- Phosphonous monoester
- Phosphonous diester
- Phosphonous monoamide
- Phosphonous diamide
- Phosphonous esteramide
- Phosphonous derivatives
- Phosphinous acid
- Phosphinous ester
- Phosphinous amide
- Phosphinous derivatives
- II.4 Silicon
- Quart silane
- Non-quart silane
- Silylmonohalide
- Het trialkylsilane
- Dihet dialkylsilane
- Trihet alkylsilane
- Silicic acid derivative
- II.5 Boron
- Trialkylborane
- Boric acid derivatives
- Boronic acid derivative
- Borohydride
- Quaternary boron
Part III: Some Special Patterns
- III.1 Chains
- III.2 Rings
- Aromatic
- Heterocyclic
- Epoxide
- NH aziridine
- Spiro
- Annelated rings
- Bridged rings
- III.3 Sugars and Nucleosides/Nucleotides, Steroids
- Sugar pattern 1
- Sugar pattern 2
- Sugar pattern combi
- Sugar pattern 2 reducing
- Sugar pattern 2 alpha
- Sugar pattern 2 beta
- III.4 Everything else...
- Conjugated double bond
- Conjugated tripple bond
- Cis double bond
- Trans double bond
- Mixed anhydrides
- Halogen on hetero
- Halogen multi subst
- Trifluoromethyl
- C ONS bond
- Charged
- Anion
- Kation
- Salt
- 1,3-Tautomerizable
- 1,5-Tautomerizable
- Rotatable bond
- Michael acceptor
- Dicarbodiazene
- CH-acidic
- CH-acidic strong
- Chiral center specified