accessibility menu, dialog, popup

UserName
Viewing profile as user:

Unclassified Organic Compounds

Organic compounds that do not fit into any other organic chemical classification.
Quantity 
  • (1)
  • (10)
  • (1)
  • (1)
  • (7)
  • (1)
  • (7)
  • (2)
  • (9)
  • (3)
  • (3)
  • (8)
  • (1)
  • (6)
  • (1)
  • (2)
  • (1)
  • (1)
Molecular Weight (g/mol) 
  • (3)
  • (1)
  • (2)
  • (1)
  • (3)
  • (5)
  • (1)
  • (1)
  • (4)
  • (4)
  • (1)
  • (2)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (10)
  • (2)
  • (1)
  • (1)
  • (2)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
Percent Purity 
  • (1)
  • (2)
  • (1)
  • (2)
  • (2)
  • (1)
  • (4)
  • (1)
  • (2)
  • (2)
  • (6)
  • (1)
  • (7)
  • (9)
  • (1)
  • (1)
Physical Form 
  • (6)
  • (1)
  • (3)
  • (3)
  • (1)
  • (2)
  • (3)
  • (2)
Boiling Point 
  • (1)
  • (1)
  • (2)
  • (2)
  • (1)
  • (2)
  • (4)
  • (2)
  • (1)
  • (2)

Filtered Search Results

Products from some of our suppliers do not display in filtered search results. Please clear all filters to see these products.

Narrow Results

Narrow Results

category

special offers

  • (14)

brands

  • (2)
  • (1)
  • (53)
  • (2)
  • (1)
  • (1)
  • (1)
  • (8)
  • (138)
  • (4)
  • (18)
  • (1)
  • (4)
  • (24)
  • (31)
  • (6)
  • (6)
  • (19)

special interests

  • (21)

Quantity

  • (1)
  • (10)
  • (1)
  • (1)
  • (7)
  • (1)
  • (7)
  • (2)
  • (9)
  • (3)
  • (3)
  • (8)
  • (1)
  • (6)
  • (1)
  • (2)
  • (1)
  • (1)

Molecular Weight (g/mol)

  • (3)
  • (1)
  • (2)
  • (1)
  • (3)
  • (5)
  • (1)
  • (1)
  • (4)
  • (4)
  • (1)
  • (2)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (10)
  • (2)
  • (1)
  • (1)
  • (2)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)
  • (1)

Percent Purity

  • (1)
  • (2)
  • (1)
  • (2)
  • (2)
  • (1)
  • (4)
  • (1)
  • (2)
  • (2)
  • (6)
  • (1)
  • (7)
  • (9)
  • (1)
  • (1)

Physical Form

  • (6)
  • (1)
  • (3)
  • (3)
  • (1)
  • (2)
  • (3)
  • (2)

Boiling Point

  • (1)
  • (1)
  • (2)
  • (2)
  • (1)
  • (2)
  • (4)
  • (2)
  • (1)
  • (2)

Grade

  • (1)
  • (1)

Product Line

  • (1)

Search Within Results
Keyword Search:
1 – 15 of 300 results
1

Quinine Hydrochloride Dihydrate 98.0+%, TCI America™

CAS: 6119-47-7 Molecular Formula: C20H29ClN2O4 Molecular Weight (g/mol): 396.91 MDL Number: MFCD00151248 InChI Key: MPQKYZPYCSTMEI-VQYSEXPNNA-N Synonym: quinine hcl dihydrate PubChem CID: 124080947 IUPAC Name: (R)-[(2S,5R)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl](6-methoxyquinolin-4-yl)methanol dihydrate hydrochloride SMILES: O.O.Cl.[H][C@@]1(CN2CCC1C[C@@]2([H])[C@H](O)C1=C2C=C(OC)C=CC2=NC=C1)C=C

PubChem CID 124080947
CAS 6119-47-7
Molecular Weight (g/mol) 396.91
MDL Number MFCD00151248
SMILES O.O.Cl.[H][C@@]1(CN2CCC1C[C@@]2([H])[C@H](O)C1=C2C=C(OC)C=CC2=NC=C1)C=C
Synonym quinine hcl dihydrate
IUPAC Name (R)-[(2S,5R)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl](6-methoxyquinolin-4-yl)methanol dihydrate hydrochloride
InChI Key MPQKYZPYCSTMEI-VQYSEXPNNA-N
Molecular Formula C20H29ClN2O4
2

L-Thioproline 98.0+%, TCI America™

CAS: 34592-47-7 Molecular Formula: C4H7NO2S Molecular Weight (g/mol): 133.165 MDL Number: MFCD00005212 InChI Key: DZLNHFMRPBPULJ-VKHMYHEASA-N Synonym: l-thioproline,r-thiazolidine-4-carboxylic acid,l-thiaproline,l-thiazolidine-4-carboxylic acid,4r-1,3-thiazolidine-4-carboxylic acid,h-thz-oh,r-4-thiazolidinecarboxylic acid,4-thiaproline,thioproline,gamma-thioproline PubChem CID: 93176 ChEBI: CHEBI:45171 IUPAC Name: (4R)-1,3-thiazolidine-4-carboxylic acid SMILES: C1C(NCS1)C(=O)O

PubChem CID 93176
CAS 34592-47-7
Molecular Weight (g/mol) 133.165
ChEBI CHEBI:45171
MDL Number MFCD00005212
SMILES C1C(NCS1)C(=O)O
Synonym l-thioproline,r-thiazolidine-4-carboxylic acid,l-thiaproline,l-thiazolidine-4-carboxylic acid,4r-1,3-thiazolidine-4-carboxylic acid,h-thz-oh,r-4-thiazolidinecarboxylic acid,4-thiaproline,thioproline,gamma-thioproline
IUPAC Name (4R)-1,3-thiazolidine-4-carboxylic acid
InChI Key DZLNHFMRPBPULJ-VKHMYHEASA-N
Molecular Formula C4H7NO2S
3

Selectophore™ Dioctyl phenylphosphonate, MilliporeSigma™ Supelco™

MDL Number: MFCD00009561 Synonym: DOPP

MDL Number MFCD00009561
Synonym DOPP
4

4-Nitro-1,2,3,6,7,8-hexahydropyrene 98.0+%, TCI America™

CAS: 88535-47-1 Molecular Formula: C16H15NO2 Molecular Weight (g/mol): 253.301 MDL Number: MFCD27964325 InChI Key: KVZSMBRWPWEQHJ-UHFFFAOYSA-N PubChem CID: 184879 IUPAC Name: 4-nitro-1,2,3,6,7,8-hexahydropyrene SMILES: C1CC2=C3C(=CC(=C4C3=C(CCC4)C=C2)[N+](=O)[O-])C1

PubChem CID 184879
CAS 88535-47-1
Molecular Weight (g/mol) 253.301
MDL Number MFCD27964325
SMILES C1CC2=C3C(=CC(=C4C3=C(CCC4)C=C2)[N+](=O)[O-])C1
IUPAC Name 4-nitro-1,2,3,6,7,8-hexahydropyrene
InChI Key KVZSMBRWPWEQHJ-UHFFFAOYSA-N
Molecular Formula C16H15NO2
5

Quinine hydrochloride, MP Biomedicals™

CAS: 6119-47-7 Molecular Formula: C20H29ClN2O4 Molecular Weight (g/mol): 396.91 MDL Number: MFCD00151248 InChI Key: MPQKYZPYCSTMEI-VQYSEXPNNA-N Synonym: quinine hcl dihydrate PubChem CID: 124080947 IUPAC Name: (R)-[(2S,5R)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl](6-methoxyquinolin-4-yl)methanol dihydrate hydrochloride SMILES: O.O.Cl.[H][C@@]1(CN2CCC1C[C@@]2([H])[C@H](O)C1=C2C=C(OC)C=CC2=NC=C1)C=C

PubChem CID 124080947
CAS 6119-47-7
Molecular Weight (g/mol) 396.91
MDL Number MFCD00151248
SMILES O.O.Cl.[H][C@@]1(CN2CCC1C[C@@]2([H])[C@H](O)C1=C2C=C(OC)C=CC2=NC=C1)C=C
Synonym quinine hcl dihydrate
IUPAC Name (R)-[(2S,5R)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl](6-methoxyquinolin-4-yl)methanol dihydrate hydrochloride
InChI Key MPQKYZPYCSTMEI-VQYSEXPNNA-N
Molecular Formula C20H29ClN2O4
6

Quinine hydrochloride, 100.8%, >99%, MP Biomedicals™

CAS: 6119-47-7 Molecular Formula: C20H29ClN2O4 Molecular Weight (g/mol): 396.91 MDL Number: MFCD00151248 InChI Key: MPQKYZPYCSTMEI-VQYSEXPNNA-N Synonym: quinine hcl dihydrate PubChem CID: 124080947 IUPAC Name: (R)-[(2S,5R)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl](6-methoxyquinolin-4-yl)methanol dihydrate hydrochloride SMILES: O.O.Cl.[H][C@@]1(CN2CCC1C[C@@]2([H])[C@H](O)C1=C2C=C(OC)C=CC2=NC=C1)C=C

PubChem CID 124080947
CAS 6119-47-7
Molecular Weight (g/mol) 396.91
MDL Number MFCD00151248
SMILES O.O.Cl.[H][C@@]1(CN2CCC1C[C@@]2([H])[C@H](O)C1=C2C=C(OC)C=CC2=NC=C1)C=C
Synonym quinine hcl dihydrate
IUPAC Name (R)-[(2S,5R)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl](6-methoxyquinolin-4-yl)methanol dihydrate hydrochloride
InChI Key MPQKYZPYCSTMEI-VQYSEXPNNA-N
Molecular Formula C20H29ClN2O4
7
Promotions Available

Betaine monohydrate, 99+%, for analysis

CAS: 590-47-6 Molecular Formula: C5H13NO3 Molecular Weight (g/mol): 135.16 MDL Number: MFCD00150010 InChI Key: NJZRLXNBGZBREL-UHFFFAOYSA-N Synonym: betaine monohydrate,2-trimethylammonio acetate hydrate,glycine betaine hydrate,unii-tpu0itr2br,carboxymethyl trimethylammonium hydroxide,tpu0itr2br,bet hydrate,betaine, hydrate,dsstox_cid_29381,dsstox_rid_83496 PubChem CID: 134128033 IUPAC Name: carboxymethyl(trimethyl)azanium;hydroxide;hydrate SMILES: [OH-].C[N+](C)(C)CC(O)=O

PubChem CID 134128033
CAS 590-47-6
Molecular Weight (g/mol) 135.16
MDL Number MFCD00150010
SMILES [OH-].C[N+](C)(C)CC(O)=O
Synonym betaine monohydrate,2-trimethylammonio acetate hydrate,glycine betaine hydrate,unii-tpu0itr2br,carboxymethyl trimethylammonium hydroxide,tpu0itr2br,bet hydrate,betaine, hydrate,dsstox_cid_29381,dsstox_rid_83496
IUPAC Name carboxymethyl(trimethyl)azanium;hydroxide;hydrate
InChI Key NJZRLXNBGZBREL-UHFFFAOYSA-N
Molecular Formula C5H13NO3
8

N-Acetylglycine Ethyl Ester 98.0+%, TCI America™

CAS: 1906-82-7 Molecular Formula: C6H11NO3 Molecular Weight (g/mol): 145.158 MDL Number: MFCD00009173 InChI Key: AMBDTBHJFINMSE-UHFFFAOYSA-N Synonym: ethyl acetamidoacetate,ac-gly-oet,n-acetylglycine ethyl ester,ethyl n-acetylglycinate,ethylaceturate,ethyl acetaminoacetate,ethyl 2-acetylamino acetate,glycine, n-acetyl-, ethyl ester,acetylglycine ethyl ester,acetyl-glycine ethyl ester PubChem CID: 74702 IUPAC Name: ethyl 2-acetamidoacetate SMILES: CCOC(=O)CNC(=O)C

PubChem CID 74702
CAS 1906-82-7
Molecular Weight (g/mol) 145.158
MDL Number MFCD00009173
SMILES CCOC(=O)CNC(=O)C
Synonym ethyl acetamidoacetate,ac-gly-oet,n-acetylglycine ethyl ester,ethyl n-acetylglycinate,ethylaceturate,ethyl acetaminoacetate,ethyl 2-acetylamino acetate,glycine, n-acetyl-, ethyl ester,acetylglycine ethyl ester,acetyl-glycine ethyl ester
IUPAC Name ethyl 2-acetamidoacetate
InChI Key AMBDTBHJFINMSE-UHFFFAOYSA-N
Molecular Formula C6H11NO3
9

Quinine Monohydrochloride Dihydrate, 100.8%, MP Biomedicals™

CAS: 6119-47-7 Molecular Formula: C20H29ClN2O4 Molecular Weight (g/mol): 396.91 MDL Number: MFCD00151248 InChI Key: MPQKYZPYCSTMEI-VQYSEXPNNA-N Synonym: quinine hydrochloride dihydrate,quinine monohydrochloride dihydrate,cinchonan-9-ol, 6'-methoxy-, monohydrochloride, dihydrate, 8a,9r,quinine hcl dihydrate,r-2s,4s,5r-5-ethenyl-1-azabicyclo 2.2.2 octan-2-yl-6-methoxyquinolin-4-yl methanol;dihydrate;hydrochloride,chinini hydrochloridum,quinine, hcl dihydrate,quinine hydrochloride jan:nf,quinine monohydrochloride hydrate PubChem CID: 134690644 IUPAC Name: (R)-[(2S,5R)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl](6-methoxyquinolin-4-yl)methanol dihydrate hydrochloride SMILES: O.O.Cl.[H][C@@]1(CN2CCC1C[C@@]2([H])[C@H](O)C1=C2C=C(OC)C=CC2=NC=C1)C=C

PubChem CID 134690644
CAS 6119-47-7
Molecular Weight (g/mol) 396.91
MDL Number MFCD00151248
SMILES O.O.Cl.[H][C@@]1(CN2CCC1C[C@@]2([H])[C@H](O)C1=C2C=C(OC)C=CC2=NC=C1)C=C
Synonym quinine hydrochloride dihydrate,quinine monohydrochloride dihydrate,cinchonan-9-ol, 6'-methoxy-, monohydrochloride, dihydrate, 8a,9r,quinine hcl dihydrate,r-2s,4s,5r-5-ethenyl-1-azabicyclo 2.2.2 octan-2-yl-6-methoxyquinolin-4-yl methanol;dihydrate;hydrochloride,chinini hydrochloridum,quinine, hcl dihydrate,quinine hydrochloride jan:nf,quinine monohydrochloride hydrate
IUPAC Name (R)-[(2S,5R)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl](6-methoxyquinolin-4-yl)methanol dihydrate hydrochloride
InChI Key MPQKYZPYCSTMEI-VQYSEXPNNA-N
Molecular Formula C20H29ClN2O4
10
Promotions Available

Thermo Scientific Chemicals Apixaban

CAS: 503612-47-3 Molecular Formula: C25H25N5O4 Molecular Weight (g/mol): 459.51 InChI Key: QNZCBYKSOIHPEH-UHFFFAOYSA-N IUPAC Name: 1-(4-methoxyphenyl)-7-oxo-6-[4-(2-oxopiperidin-1-yl)phenyl]-1H,4H,5H,6H,7H-pyrazolo[3,4-c]pyridine-3-carboxamide SMILES: COC1=CC=C(C=C1)N1N=C(C(N)=O)C2=C1C(=O)N(CC2)C1=CC=C(C=C1)N1CCCCC1=O

CAS 503612-47-3
Molecular Weight (g/mol) 459.51
SMILES COC1=CC=C(C=C1)N1N=C(C(N)=O)C2=C1C(=O)N(CC2)C1=CC=C(C=C1)N1CCCCC1=O
IUPAC Name 1-(4-methoxyphenyl)-7-oxo-6-[4-(2-oxopiperidin-1-yl)phenyl]-1H,4H,5H,6H,7H-pyrazolo[3,4-c]pyridine-3-carboxamide
InChI Key QNZCBYKSOIHPEH-UHFFFAOYSA-N
Molecular Formula C25H25N5O4
11
Promotions Available

Quinine monohydrochloride dihydrate, 99% (total base), may contain up to 10% Dihydroquinine

CAS: 6119-47-7 Molecular Formula: C20H29ClN2O4 Molecular Weight (g/mol): 396.91 MDL Number: MFCD00151248 InChI Key: MPQKYZPYCSTMEI-VQYSEXPNNA-N Synonym: quinine hcl dihydrate PubChem CID: 124080947 IUPAC Name: (R)-[(2S,4S,5S)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl]-(6-methoxyquinolin-4-yl)methanol;dihydrate;hydrochloride SMILES: O.O.Cl.[H][C@@]1(CN2CCC1C[C@@]2([H])[C@H](O)C1=C2C=C(OC)C=CC2=NC=C1)C=C

PubChem CID 124080947
CAS 6119-47-7
Molecular Weight (g/mol) 396.91
MDL Number MFCD00151248
SMILES O.O.Cl.[H][C@@]1(CN2CCC1C[C@@]2([H])[C@H](O)C1=C2C=C(OC)C=CC2=NC=C1)C=C
Synonym quinine hcl dihydrate
IUPAC Name (R)-[(2S,4S,5S)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl]-(6-methoxyquinolin-4-yl)methanol;dihydrate;hydrochloride
InChI Key MPQKYZPYCSTMEI-VQYSEXPNNA-N
Molecular Formula C20H29ClN2O4
12
Promotions Available

Quinine monohydrochloride dihydrate, 99%

CAS: 6119-47-7 Molecular Formula: C20H29ClN2O4 Molecular Weight (g/mol): 396.91 MDL Number: MFCD00151248 InChI Key: MPQKYZPYCSTMEI-VQYSEXPNNA-N Synonym: quinine hcl dihydrate PubChem CID: 124080947 IUPAC Name: (R)-[(2S,4S,5S)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl]-(6-methoxyquinolin-4-yl)methanol;dihydrate;hydrochloride SMILES: O.O.Cl.[H][C@@]1(CN2CCC1C[C@@]2([H])[C@H](O)C1=C2C=C(OC)C=CC2=NC=C1)C=C

PubChem CID 124080947
CAS 6119-47-7
Molecular Weight (g/mol) 396.91
MDL Number MFCD00151248
SMILES O.O.Cl.[H][C@@]1(CN2CCC1C[C@@]2([H])[C@H](O)C1=C2C=C(OC)C=CC2=NC=C1)C=C
Synonym quinine hcl dihydrate
IUPAC Name (R)-[(2S,4S,5S)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl]-(6-methoxyquinolin-4-yl)methanol;dihydrate;hydrochloride
InChI Key MPQKYZPYCSTMEI-VQYSEXPNNA-N
Molecular Formula C20H29ClN2O4
13
Promotions Available

L-Thiazolidine-4-carboxylic acid, 98%

CAS: 34592-47-7 Molecular Formula: C4H7NO2S Molecular Weight (g/mol): 133.165 MDL Number: MFCD00005212 InChI Key: DZLNHFMRPBPULJ-VKHMYHEASA-N Synonym: l-thioproline,r-thiazolidine-4-carboxylic acid,l-thiaproline,l-thiazolidine-4-carboxylic acid,4r-1,3-thiazolidine-4-carboxylic acid,h-thz-oh,r-4-thiazolidinecarboxylic acid,4-thiaproline,thioproline,gamma-thioproline PubChem CID: 93176 ChEBI: CHEBI:45171 IUPAC Name: (4R)-1,3-thiazolidine-4-carboxylic acid SMILES: C1C(NCS1)C(=O)O

PubChem CID 93176
CAS 34592-47-7
Molecular Weight (g/mol) 133.165
ChEBI CHEBI:45171
MDL Number MFCD00005212
SMILES C1C(NCS1)C(=O)O
Synonym l-thioproline,r-thiazolidine-4-carboxylic acid,l-thiaproline,l-thiazolidine-4-carboxylic acid,4r-1,3-thiazolidine-4-carboxylic acid,h-thz-oh,r-4-thiazolidinecarboxylic acid,4-thiaproline,thioproline,gamma-thioproline
IUPAC Name (4R)-1,3-thiazolidine-4-carboxylic acid
InChI Key DZLNHFMRPBPULJ-VKHMYHEASA-N
Molecular Formula C4H7NO2S
14
Promotions Available

Ethyl (S)-(+)-2-pyrrolidone-5-carboxylate, 99%

CAS: 7149-65-7 Molecular Formula: C7H11NO3 Molecular Weight (g/mol): 157.16 MDL Number: MFCD00064497 InChI Key: QYJOOVQLTTVTJY-YFKPBYRVSA-N Synonym: l-pyroglutamic acid ethyl ester,ethyl s-+-2-pyrrolidone-5-carboxylate,s-ethyl 5-oxopyrrolidine-2-carboxylate,ethyl 2s-5-oxopyrrolidine-2-carboxylate,ethyl l-pyroglutamate,ethyl pidolate,h-pyr-oet,ethyl 5-oxo-l-prolinate,ethyl pyroglutamate,unii-1ps59es316 PubChem CID: 2724446 IUPAC Name: ethyl (2S)-5-oxopyrrolidine-2-carboxylate SMILES: CCOC(=O)C1CCC(=O)N1

PubChem CID 2724446
CAS 7149-65-7
Molecular Weight (g/mol) 157.16
MDL Number MFCD00064497
SMILES CCOC(=O)C1CCC(=O)N1
Synonym l-pyroglutamic acid ethyl ester,ethyl s-+-2-pyrrolidone-5-carboxylate,s-ethyl 5-oxopyrrolidine-2-carboxylate,ethyl 2s-5-oxopyrrolidine-2-carboxylate,ethyl l-pyroglutamate,ethyl pidolate,h-pyr-oet,ethyl 5-oxo-l-prolinate,ethyl pyroglutamate,unii-1ps59es316
IUPAC Name ethyl (2S)-5-oxopyrrolidine-2-carboxylate
InChI Key QYJOOVQLTTVTJY-YFKPBYRVSA-N
Molecular Formula C7H11NO3
15

L(-)-Thiazolidine-4-carboxylic acid, 98%

CAS: 34592-47-7 Molecular Formula: C4H7NO2S Molecular Weight (g/mol): 133.16 MDL Number: MFCD00005212 InChI Key: DZLNHFMRPBPULJ-VKHMYHEASA-N Synonym: l-thioproline,r-thiazolidine-4-carboxylic acid,l-thiaproline,l-thiazolidine-4-carboxylic acid,4r-1,3-thiazolidine-4-carboxylic acid,h-thz-oh,r-4-thiazolidinecarboxylic acid,4-thiaproline,thioproline,gamma-thioproline PubChem CID: 93176 ChEBI: CHEBI:45171 IUPAC Name: (4R)-1,3-thiazolidine-4-carboxylic acid SMILES: C1C(NCS1)C(=O)O

PubChem CID 93176
CAS 34592-47-7
Molecular Weight (g/mol) 133.16
ChEBI CHEBI:45171
MDL Number MFCD00005212
SMILES C1C(NCS1)C(=O)O
Synonym l-thioproline,r-thiazolidine-4-carboxylic acid,l-thiaproline,l-thiazolidine-4-carboxylic acid,4r-1,3-thiazolidine-4-carboxylic acid,h-thz-oh,r-4-thiazolidinecarboxylic acid,4-thiaproline,thioproline,gamma-thioproline
IUPAC Name (4R)-1,3-thiazolidine-4-carboxylic acid
InChI Key DZLNHFMRPBPULJ-VKHMYHEASA-N
Molecular Formula C4H7NO2S