2,3,4-Trihydroxybenzophenone(1143-72-2)
- Name: 2,3,4-Trihydroxybenzophenone
- Synonyms:Benzophenone,2,3,4-trihydroxy- (7CI,8CI);Alizarin Yellow A;Alizarine Yellow A;C.I. 57005;Gallobenzophenone;NSC 30665;PHF 005;
- Molecular Formula:C13H10O4
- Molecular Weight:230.22
- CAS Registry Number:1143-72-2
- EINECS:214-540-1
- Melting Point:139-141 °C
- Water Solubility:13.22g/L(24.99 oC)
CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:98.0% Appearance:Light yellow or yellow powder Application:As organic intermediates, used in microelectronic integrated circuit (IC) industry photoresist, pharmaceutical intermediates, UV absorber.
Min. Order:0Metric Ton
Supplier:Shanghai Dynamic Industrial Co.,Ltd. [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:98% Appearance:Showed in specifications Package:according to the clients requirement Storage:Store in dry, dark and ventilated place. Transportation:by sea or by air Application:It is an important raw material and intermediate used in Organic Synthesis, Pharmaceuticals, Agrochemicals and Dyestuff.
Min. Order:1Kilogram
Supplier:Dayang Chem (Hangzhou) Co.,Ltd. [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:99% Appearance:Light yellow powder Package:25kg/drum or at customers requirement. Storage:R.T. Transportation:Express/Sea/Air Application:used as organic intermediates, photoresists, pharmaceutical intermediates, ultraviolet light absorbers, etc. in the microelectronic integrated circuit (IC) industry.
Min. Order:1Kilogram
Supplier:Hangzhou Sartort Biopharma Co., Ltd [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:鈮?9% Appearance:Yellowish to off-white powder Package:25kg/drum Storage:cool and seal Transportation:by sea, by air, by courier Application:UV absorber, electronic material and pharmaceutical intermediate
Min. Order:100Gram
Supplier:Jinan Finer Chemical Co., Ltd [
China (Mainland)] CAS No.1143-72-2 Newblue-CHEM CAS:1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:99% Appearance:White powder Package:in aluminium foil bag Storage:stored in a cool, dry and ventilated place Transportation:sea Application:pharma
Min. Order:100Metric Ton
Supplier:HENAN NEW BLUE CHEMICAL CO.,LTD [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:98% Appearance:Powder Package:according to the need of packing Storage:Store below +30掳C. Transportation:air sea or courier Application:intermediate
Min. Order:1Gram
Supplier:Shanghai Minstar Chemical Co., Ltd [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:99% Package:According to customer requirements Transportation:By Sea/Air/Courier Application:medicine
Min. Order:10Gram
Supplier:Zibo Hangyu Biotechnology Development Co., Ltd [
China (Mainland)] CAS No.1143-72-2 High Quality 2,3,4-Triphdroxy Benzophenone in stock
Assay:99% Appearance:Yellow crystalline powder Package:25kg/bag Storage:Cool and dry place Transportation:by sea or by air, express for small quantity Application:CAS: 1143-72-2
Min. Order:1Kilogram
Supplier:Siwei Development Group Ltd. [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:99% Package:According client's requirements Transportation:by sea/by air/by courier Application:Chemical products
Min. Order:1Kilogram
Supplier:Hangzhou ZeErRui Chemical Co., Ltd. [
China (Mainland)] CAS No.1143-72-2 Fast Delivery 1143-72-2 in bulk supply 2,3,4-Trihydroxybenzophenone in china
Assay:99% Appearance:Yellow crystalline powder Package:according to customers' requirements Storage:Sealed in dry,Room Temperature Transportation:By air(EMS or EUB or FedEx or TNT ect...) or by sea(FOB or CIF or CNF ect...)or according to your demand. Application:used as an organic intermediate for photoresists, pharmaceutical intermediates, ultraviolet absorbers, etc. in the microelectronic integrated circuit (IC) industry
Min. Order:1Gram
Supplier:Hangzhou Lingrui Chemical Co.,Ltd. [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone 1143-72-2
Assay:鈮?9% Appearance:White powder Package:Bagged or according to your request Storage:Sealed in dry,Room Temperature Transportation:Transport锛? EMS,DHL, TNT, UPS ,FEDEX, BY AIR, BY SEA DHL Express, FedEx and EMS for quantity less than 50KG, usually called as DDU service; Sea shipping for quantity over 500KG; And air shipping i Application:Used as organic intermediates, photoresist, pharmaceutical intermediates, UV absorbers and so on for microelectronics integrated circuit (IC) industry
Min. Order:1Kilogram
Supplier:Hebei Nengqian Chemical Import and Export Co., LTD [
China (Mainland)] CAS No.1143-72-2 High quality 2,3,4-Trihydroxybenzophenone supplier in China
Assay:99% Appearance:white-off solid or colorless liquid ( referto COA) Package:25kgs/fiber drum or 200kgs/UN drum Storage:in a cool and dry place Transportation:by sea or by air Application:Intermediate
Min. Order:0Metric Ton
Supplier:Simagchem Corporation [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:99.0% Appearance:liquid Package:Grams, Kilograms Storage:Store the container tightly closed in a dry, cool and well-ventilated place. Store apart from foodstuff containers or incompatible materials. Transportation:According to customer request Application:For R&D and commerical use
Min. Order:100Gram
Supplier:Chemlyte Solutions [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay: 98%Min Appearance:Detailed in specifications Package:According to customer Storage:Store in dry, dark and ventilated place Transportation:By air or by sea Application:An important raw material and intermediate used in organic Synthesis, Pharmaceuticals
Min. Order:1Kilogram
Supplier:TAIZHOU ZHENYU BIOTECHNOLOGY CO., LTD [
China (Mainland)] CAS No.1143-72-2 Methanone,phenyl(2,3,4-trihydroxyphenyl)-
Assay:99% Appearance:White fine powder Package:according to the clients requirement Storage:Store in dry dark and ventilated place Transportation:Transportation by express, air, sea; port mainly to Qingdao / Tianjin / Shanghai, or according to customer needs to send different ports and aviation. Application:It is an important raw material.
Min. Order:1Kilogram
Supplier:Shandong Hanjiang Chemical Co., Ltd. [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone.
Assay:99% Appearance:white powder Package:as per your request Storage:Stored in cool, dry and ventilation place; Away from fire and heat Transportation:as per your request. Application:Used as Pharmaceutical Intermediates, etc.
Min. Order:1Kilogram
Supplier:HANGZHOU YUNUO CHEMICAL CO.,LTD [
China (Mainland)] CAS No.1143-72-2 Best price 2,3,4-Trihydroxybenzophenone 1143-72-2
Assay:99.5% Appearance:white or almost white crystalline powder Package:Pack & Store:25kg cardboard barrels lined with plastic bags; or otherwise customized Storage:In cool ,dry place Transportation:Preservce in well-closed containers, prptected from light, Application:USP34 Or EP STANDERUsed as Antibiotic and Antimicrobial Agents
Min. Order:100Kilogram
Supplier:Lonwin Chemical Group Limited [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:鈮?8% Appearance:powder Package:BAG Storage:In cool ,dry place Transportation:Air or sea freight Application:for pharma use
Min. Order:1Kilogram
Supplier:Qingdao Chengyuan Kaisheng Industry and Trade Co., Ltd. [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:HPLC鈮?8% Appearance:powder Storage:Sealed in dry,Room Temperature Transportation:by express or by sea Application:for pharma use
Min. Order:0
Supplier:Hangzhou Shanyi Biotechnology Co., Ltd. [
China (Mainland)] CAS No.1143-72-2 Methanone,phenyl(2,3,4-trihydroxyphenyl)-
Assay:0.98 Appearance:Off white to slight yellow solid Package:1L 5L 10L 25L bottle Storage:Stored in shaded, cool and dry places Transportation:Handle with cares to avoid damaging the packages. Protect them from sunshine or rain. We can send by Fedex, by ship or by plane according to international rules. Application:pharma intermediate
Min. Order:0
Supplier:Antimex Chemical Limied [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:98%,99% Appearance:refer to COA Package:According to the clients requirement Storage:Store in dry, cool and ventilated place Transportation:By sea or by air or by courier Application:Liquid crystal intermediate
Min. Order:0
Supplier:Hangzhou Ocean Chemical Co., Ltd. [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:98% Application:intermediate
Min. Order:0
Supplier:SAGECHEM LIMITED [
China (Mainland)] CAS No.1143-72-2 Phenyl(2,3,4-trihydroxyphenyl)methanone
Assay:99% Appearance:Solid Storage:Protect from light and keep dry Application:Pharmaceutical intermediates
Min. Order:0
Supplier:ORCHID CHEMICAL SUPPLIES LTD [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:98% Package:25kg/drum,or as per customers'demand Transportation:air,sea,courier Application:API,Pharmaceutical intermediates
Min. Order:0
Supplier:GIHI CHEMICALS CO.,LIMITED [
China (Mainland)] CAS No.1143-72-2 Methanone,phenyl(2,3,4-trihydroxyphenyl)-
Assay:98%min Appearance:Off-white to light yellow powder Package:According to the clients requirement. Storage:Keep in cool place. Transportation:Sea/air/courier Application:Pharmaceutical intermediates
Min. Order:0
Supplier:Hangzhou J&H Chemical Co., Ltd. [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:99.0% min Appearance:Highest quality appearance Package:25kgs/drum锛?00kg/drum锛汭BC TANK Storage:Keep in dry and well ventilated warehouse, keep sealed Transportation:By air and by sea Application:Extremely good quality, widely used in Pharmaceutical Industry, Food Industry, agricultural industry etc.
Min. Order:1Kilogram
Supplier:Hangzhou Johoo Chemical Co., Ltd [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:99% Package:box or opp package Storage:cool drum Transportation:air or sea Application:2,3,4-Trihydroxybenzophenone
Min. Order:1Milligram
Supplier:weifang yangxu group co.,ltd [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:HPLC鈮?8% Appearance:White powder or granule Package:25kg drum/bag Storage:Keep in dry and cool place Transportation:by Sea, air and express Application:Used as a calcium booster in the food industry
Min. Order:1Metric Ton
Supplier:KAISA GROUP INC [
United States] CAS No.1143-72-2 Methanone,phenyl(2,3,4-trihydroxyphenyl)-
Assay:99% Package:drum Transportation:By Sea/Air/DHL Application:Henan Wentao Chemical Product Co., Ltd.
Min. Order:0
Supplier:Henan Wentao Chemical Product Co., Ltd. [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:99% Appearance:detailed see specifications Package:25kg/drum;200kg/drum Storage:Keep away of light, cool place Transportation:Sea/air/courier Application:Chemical synthesis
Min. Order:0
Supplier:Xiamen Hisunny Chemical Co.,Ltd [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:99 Appearance:off white Package:drum Storage:Dry,cool place Transportation:by air/sea/express Application:active pharmaceutical ingredients
Min. Order:0
Supplier:Hubei Vanz Pharm Co.,Ltd [
China (Mainland)] CAS No.1143-72-2 2,3,4-TRIHYDROXYBENZOPHENONE
Assay:99% Package:1kg/bag; 455kg/drum, or as customer's request. Transportation:DHL, EMS, FedEx, TNT, AIR, SEA Application:Xiamen Luyunjia Trading Co.,Ltd
Min. Order:0
Supplier:Luyunjia Chemistry Xiamen Limited [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:99% Appearance:white powder Package:25kg,50kg,180kg,200kg,250kg,1000kg锛宑ustomization Storage:Keep it in dry,shady and cool place Transportation:by express or by sea Application:Pharma;Industry;Agricultural;chemical reaserch
Min. Order:0
Supplier:Wuhan Circle Star Chem-medical Technology co.,Ltd. [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:COA Appearance:COA Storage:in stock Application:MSDS/TDS
Min. Order:0
Supplier:Aecochem Corp. [
China (Mainland)] CAS No.1143-72-2 1143-72-2
Assay:99% Application:api
Min. Order:0
Supplier:Jilin Artel New Materials Co., LTD [
China (Mainland)] CAS No.1143-72-2 Top Purity CAS 1143-72-2 with fast shipping
Assay:99% Appearance:White powder Package: [Packaging]20mg, 50mg,100mg,1g,10g,100g,according to customers' requirements Storage: should be stored in a well-closed container at low temperature, keep away from moisture, heat and light. Transportation:1. Samples 1kg-10kg are shipped by international express. 2. 50kg-100kg of goods are transported by dedicated line logistics. 3. Cargo 100kg-1ton is transported by dedicated line logistics. Application:Chemical raw materials, pharmaceutical intermediates, cosmetic raw materials, etc.
Min. Order:1Kilogram
Supplier:Zhuozhou Wenxi import and Export Co., Ltd [
China (Mainland)] CAS No.1143-72-2 Factory Supply 2,3,4-trihydroxybenzophenone
Assay:99.9% Appearance:Refer to COA Package:drum Storage:keep in cool and dry place Transportation:by sea or by air Application:Intermediates and materials
Min. Order:1
Supplier:Ality Chemical Corporation [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:99% Appearance:powder/liquid Package:According to client's requirements Storage:Store in dry, dark and ventilated place. Transportation:by sea/by air/by express Application:pharmaceutical intermediates
Min. Order:1Gram
Supplier:Hangzhou KieRay Chem Co.,Ltd. [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone CAS 1143-72-2 IN Stock 2,3,4-Triphydroxy benzophenone CAS 1143-72-2
Assay:99% Haccp,,Halal,SC US FDA GMP ISO14001 Appearance:As per Certificate of analysis and our TDS, MSDS Package:Export standard and according to the clients requirement Storage:Store in dry, dark and ventilated place;ISO / Kosher /GMP licence commercial bulk capacity factory in China Transportation:By AIR or by SEA GMP licence / US-FDA,South Korea-KFDA Application:It is an important raw material and intermediate for chemical industry.
Min. Order:5Kiloliter
Supplier:Chemwill Asia Co., Ltd. [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:99.0% Appearance:Clear, colorless liquid Package:according to your requirement Storage:Store in a dry, dark and ventilated place Transportation:by air/by sea /by train Application:lt is an important raw material and intermediate used in Organic Synthesis, Pharmaceuticals, Agrochemicals and Dyestuff.
Min. Order:1Kilogram
Supplier:Suzhou Senfeida Chemical Co., Ltd [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:97% Appearance:Powder or liquid Package:According to customer Storage:Store in a tightly closed container, in a cool and dry place. Transportation:Fedex,DHL,TNT,BY SEA and BY AIR Application:Medicinal Chemistry Biomedicine Pharmaceutical intermediates Chemistry experiment Biological experiments Chemical reagent For R&D use only.
Min. Order:10Milligram
Supplier:Amadis Chemical Co., Ltd. [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:99% Appearance:White to light yellow to light orange fluffy powder Package:according to your requirement Storage:White to light yellow to light orange fluffy powder Transportation:by air /by train/by sea Application:lab
Min. Order:1Kilogram
Supplier:Jiangsu Xinsu New Materials Co., Ltd. [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:97% Appearance:white powder Package:according to the clients requirement Storage:Room temperature with sealed well Transportation:by sea or by air Application:Use as primary and secondary intermediate
Min. Order:0
Supplier:BOC Sciences [
United States] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:98% Package:As client requirement Transportation:Express, Air , Sea shipment Application:Pharmaceutical Intermediates
Min. Order:0
Supplier:Hunan chemfish Pharmaceutical co.,Ltd [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone 1143-72-2
Assay:97% Appearance:solid or liquid Package:Foil bag; Drum; Plastic bottle Storage:in sealed air resistant place Transportation:by sea or air Application:Pharma;Industry;Agricultural
Min. Order:0
Supplier:Hunan Russell Chemicals Technology Co.,Ltd [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone CAS No.1143-72-2
Assay:99.90% Appearance:solid or liquid Package:As customer's requested Storage:sealed in cool and dry place Transportation:by courier/air/sea Application:Pharma Intermediate
Min. Order:0
Supplier:Guangdong Juda Chemical Industrial Co.,Limited [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:98% Package:25kg/50kg/200kg drum or Customer demand Storage:Keep away from heat,sparks and flames. Transportation:BY sea/air or by courier Application:Used as pharmaceutical intermediates
Min. Order:0
Supplier:Wuhan Fortuna Chemical Co.,Ltd [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:HPLC鈮?8% Appearance:powder Storage:Sealed in dry,Room Temperature Transportation:by express or by sea Application:for pharma use
Min. Order:0
Supplier:Falcon Life Sciences Pvt. Ltd [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:HPLC鈮?8% Appearance:powder Storage:In cool ,dry place Transportation:Air or sea freight Application:for pharma use
Min. Order:0
Supplier:Hebei Luosen New Material Technology Co., Ltd [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone manufacturer
Assay:98% Appearance:White powder Package:According client's requirements Storage:keep sealed and keep from direct light Transportation:by express or by sea Application:pharmaceutical
Min. Order:0
Supplier:Shanghai Yuanye Bio-Technology Co., Ltd. [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone cas no. 1143-72-2 98%
Assay:0.98 Package:Grams, Kilograms Transportation:According to customer request Application:For R&D
Min. Order:0
Supplier:Win-Win chemical Co.Ltd [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:99% Application:It is an important raw material.
Min. Order:0
Supplier:Shandong Mopai Biotechnology Co., LTD [
China (Mainland)] CAS No.1143-72-2 2,3,4-Trihydroxybenzophenone
Assay:98% Package:According to the demand of customer Storage:Sealed, dry, microtherm , avoid light and smell. Transportation:by air or by sea Application:Organic synthesis
Min. Order:0
Supplier:Henan Allgreen Chemical Co.,Ltd [
China (Mainland)] - Shanghai Dynamic Industrial Co.,Ltd.
- Dayang Chem (Hangzhou) Co.,Ltd.
- Hangzhou Sartort Biopharma Co., Ltd
- HENAN NEW BLUE CHEMICAL CO.,LTD
- Xiamen Hisunny Chemical Co.,Ltd
- HANGZHOU YUNUO CHEMICAL CO.,LTD
Other Product
- 443-48-1/Metronidazole
- 157496-83-8/[(2R,3S,4R,5R)-5-[6-amino-1-[(2R,3R,4S,5R)-3,4-dihydroxy-5-(phosphonooxymethyl)tetrahydrofuran-2-yl]-2H-purin-9-yl]-3,4-dihydroxy-tetrahydrofuran-2-yl]methyl (hydroxy-phosphonooxy-phosphoryl) hydrogen phosphate
- 12751-22-3/Iron phosphide
- 67893-46-3/sodium 3-[[4-acetamidophenyl]azo]-6-amino-4-hydroxynaphthalene-2-sulphonate
- 75-55-8/2-Methylaziridine
- 3623-05-0/4-Methyl-ε-caprolactam
- 1314-91-6/LEAD TELLURIDE
- 26710-98-5/Hexanedioic acid, polymer with 1,2-ethanediol, 1,1-methylenebis4-isocyanatobenzene and 1,2-propanediol
- 80419-61-0/N~6~-(acridin-9-yl)-L-lysyl-N-(8-{[(2S)-1-{[N~6~-(acridin-9-yl)-L-lysyl]amino}-6-amino-1-oxohexan-2-yl]amino}octyl)-L-lysinamide
- 35812-01-2/N-BROMOSACCHARIN
- 41451-87-0/turkesterone
- 64814-15-9/1'H-Androst-16-eno[16,17-b]pyrrole(9CI)
- 16809-60-2/2-[4-bromo-5-methyl-2-(propan-2-yl)phenoxy]-N,N-dimethylethanamine hydrochloride (1:1)
- 174740-50-2/(3S)-3-[(8-{[(3beta)-3-hydroxy-28-oxolup-20(29)-en-28-yl]amino}octanoyl)amino]-3-phenylpropanoic acid
- 6416-25-7/44BIS24DIMETHOXYBENZAMIDO22STILBENEDISULPHONICACIDDISODIUMSALT
- 1143-72-2/2,3,4-Trihydroxybenzophenone
- 99021-83-7/N-bis(dimethylamino)phosphanyl-N-methyl-methanamine; gold(+1) cation; chloride
- 2972-02-3/Cyclononanone oxime
- 66085-55-0/66085-55-0
- 4119-81-7/N-[bis(aziridin-1-yl)phosphoryl]-2-iodobenzamide
- 182155-00-6/Thiomarinol E
- 86360-33-0/MD 770207
- 8070-76-6/NITAZIN
- 32514-69-5/4-chloro-1-{1-[2-(2-ethoxyethoxy)ethoxy]ethoxy}-2-methylbenzene
- 112122-50-6/2-(4-nitrophenoxy)-N-[(2Z)-4-oxo-2-(phenylimino)-1,3-thiazolidin-3-yl]acetamide
- 64236-14-2/5-(4-methoxyphenyl)-4,6-dimethylpyrimidin-2-amine
- 17575-20-1/LANATOSIDE A
- 144-02-5/5,5-Diethylbarbituric acid sodium salt
- 26658-42-4/Colestipol HCl
- 67367-88-8/N-benzyl-N-[(1,2,3,5,6,7-hexahydro-s-indacen-4-ylmethoxy)methyl]propan-2-amine (2Z)-but-2-enedioate