摩熵化学
数据库官网
小程序
打开微信扫一扫
首页 分子通 化学资讯 化学百科 反应查询 关于我们
请输入关键词

苯酚醚

相关化合物

中文名称 英文名称 CAS号 化学式 结构式图片
—— ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-2-[(3-prop-2-enoxyphenyl)methylidene]-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C30H32N2O6S
ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-2-[(3-prop-2-enoxyphenyl)methylidene]-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-2-[[4-(dimethylamino)phenyl]methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C29H33N3O5S
ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-2-[[4-(dimethylamino)phenyl]methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-2-[(4-ethoxy-3-methoxyphenyl)methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C30H34N2O7S
ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-2-[(4-ethoxy-3-methoxyphenyl)methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-2-[(3-ethoxy-4-hydroxyphenyl)methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C29H32N2O7S
ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-2-[(3-ethoxy-4-hydroxyphenyl)methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5S)-2-[(5-bromo-2-hydroxyphenyl)methylidene]-5-(2-ethoxyphenyl)-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C25H23BrN2O5S
ethyl (2Z,5S)-2-[(5-bromo-2-hydroxyphenyl)methylidene]-5-(2-ethoxyphenyl)-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— 2-[[4-[(Z)-[(2,6-dipyrrolidin-1-ylpyrimidin-4-yl)hydrazinylidene]methyl]-2-ethoxyphenoxy]methyl]benzonitrile —— C29H33N7O2
2-[[4-[(Z)-[(2,6-dipyrrolidin-1-ylpyrimidin-4-yl)hydrazinylidene]methyl]-2-ethoxyphenoxy]methyl]benzonitrile
—— (E)-isopropyl 6-(2-methoxystyryl)-8-methyl-4-oxo-2,3,4,6-tetrahydropyrimido[2,1-b][1,3]thiazine-7-carboxylate —— C21H24N2O4S
(E)-isopropyl 6-(2-methoxystyryl)-8-methyl-4-oxo-2,3,4,6-tetrahydropyrimido[2,1-b][1,3]thiazine-7-carboxylate
—— 2-(4-chloro-3,5-dimethylphenoxy)-N-[(Z)-[(E)-4-(furan-2-yl)but-3-en-2-ylidene]amino]acetamide —— C18H19ClN2O3
2-(4-chloro-3,5-dimethylphenoxy)-N-[(Z)-[(E)-4-(furan-2-yl)but-3-en-2-ylidene]amino]acetamide
—— 2-({2-bromo-6-ethoxy-4-[(E)-{(2Z)-2-[(4-ethylphenyl)imino]-4-oxo-1,3-thiazolidin-5-ylidene}methyl]phenoxy}methyl)benzonitrile —— C28H24BrN3O3S
2-({2-bromo-6-ethoxy-4-[(E)-{(2Z)-2-[(4-ethylphenyl)imino]-4-oxo-1,3-thiazolidin-5-ylidene}methyl]phenoxy}methyl)benzonitrile
—— (2E)-2-[(4-ethoxy-3-methoxyphenyl)methylidene]-6-methyl-[1,3]thiazolo[3,2-b][1,2,4]triazine-3,7-dione —— C16H15N3O4S
(2E)-2-[(4-ethoxy-3-methoxyphenyl)methylidene]-6-methyl-[1,3]thiazolo[3,2-b][1,2,4]triazine-3,7-dione
—— ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-2-[[4-(diethylamino)phenyl]methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C31H37N3O5S
ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-2-[[4-(diethylamino)phenyl]methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-2-[(4-phenylmethoxyphenyl)methylidene]-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C34H34N2O6S
ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-2-[(4-phenylmethoxyphenyl)methylidene]-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-2-[(3-methoxy-4-methylphenyl)methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C29H32N2O6S
ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-2-[(3-methoxy-4-methylphenyl)methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2E,5R)-2-[[4-[(4-chlorophenyl)methoxy]-3-methoxyphenyl]methylidene]-7-methyl-5-(4-methylsulfanylphenyl)-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C32H29ClN2O5S2
ethyl (2E,5R)-2-[[4-[(4-chlorophenyl)methoxy]-3-methoxyphenyl]methylidene]-7-methyl-5-(4-methylsulfanylphenyl)-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-2-[(4-ethoxy-3-methoxyphenyl)methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C30H34N2O7S
ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-2-[(4-ethoxy-3-methoxyphenyl)methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5S)-2-[(4-bromophenyl)methylidene]-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C27H27BrN2O5S
ethyl (2Z,5S)-2-[(4-bromophenyl)methylidene]-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-2-[(4-phenylmethoxyphenyl)methylidene]-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C34H34N2O6S
ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-2-[(4-phenylmethoxyphenyl)methylidene]-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-2-[(3-ethoxy-4-methoxyphenyl)methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C30H34N2O7S
ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-2-[(3-ethoxy-4-methoxyphenyl)methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-2-[(4-prop-2-enoxyphenyl)methylidene]-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C30H32N2O6S
ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-2-[(4-prop-2-enoxyphenyl)methylidene]-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-2-[(3-ethoxy-4-methoxyphenyl)methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C30H34N2O7S
ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-2-[(3-ethoxy-4-methoxyphenyl)methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5R)-2-[(4-bromophenyl)methylidene]-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C27H27BrN2O5S
ethyl (2Z,5R)-2-[(4-bromophenyl)methylidene]-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-2-[(2-prop-2-enoxyphenyl)methylidene]-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C30H32N2O6S
ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-2-[(2-prop-2-enoxyphenyl)methylidene]-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5R)-2-[(5-chloro-2-hydroxyphenyl)methylidene]-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C27H27ClN2O6S
ethyl (2Z,5R)-2-[(5-chloro-2-hydroxyphenyl)methylidene]-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-2-[(3-prop-2-enoxyphenyl)methylidene]-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C30H32N2O6S
ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-2-[(3-prop-2-enoxyphenyl)methylidene]-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-2-[(3-methoxy-4-methylphenyl)methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C29H32N2O6S
ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-2-[(3-methoxy-4-methylphenyl)methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-2-[(3-ethoxy-4-hydroxyphenyl)methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C29H32N2O7S
ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-2-[(3-ethoxy-4-hydroxyphenyl)methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— N-[(Z)-(2,4-dibromo-5-hydroxyphenyl)methylideneamino]-2-(2,3,6-trimethylphenoxy)acetamide —— C18H18Br2N2O3
N-[(Z)-(2,4-dibromo-5-hydroxyphenyl)methylideneamino]-2-(2,3,6-trimethylphenoxy)acetamide
—— (5Z)-5-[[3-bromo-4-[(4-chlorophenyl)methoxy]-5-ethoxyphenyl]methylidene]-3-methyl-2-sulfanylidene-1,3-thiazolidin-4-one —— C20H17BrClNO3S2
(5Z)-5-[[3-bromo-4-[(4-chlorophenyl)methoxy]-5-ethoxyphenyl]methylidene]-3-methyl-2-sulfanylidene-1,3-thiazolidin-4-one
—— (5Z)-3-(1,1-dioxidotetrahydrothiophen-3-yl)-2-thioxo-5-(3,4,5-trimethoxybenzylidene)-1,3-thiazolidin-4-one —— C17H19NO6S3
(5Z)-3-(1,1-dioxidotetrahydrothiophen-3-yl)-2-thioxo-5-(3,4,5-trimethoxybenzylidene)-1,3-thiazolidin-4-one
—— ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-2-[[4-(diethylamino)-2-methoxyphenyl]methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C32H39N3O6S
ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-2-[[4-(diethylamino)-2-methoxyphenyl]methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-2-[(4-prop-2-enoxyphenyl)methylidene]-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C30H32N2O6S
ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-2-[(4-prop-2-enoxyphenyl)methylidene]-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-2-[[4-(diethylamino)-2-hydroxyphenyl]methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C31H37N3O6S
ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-2-[[4-(diethylamino)-2-hydroxyphenyl]methylidene]-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-7-methyl-2-[(4-methylsulfanylphenyl)methylidene]-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C28H30N2O5S2
ethyl (2Z,5S)-5-(3,4-diethoxyphenyl)-7-methyl-2-[(4-methylsulfanylphenyl)methylidene]-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5S)-2-[(5-chloro-2-hydroxyphenyl)methylidene]-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C27H27ClN2O6S
ethyl (2Z,5S)-2-[(5-chloro-2-hydroxyphenyl)methylidene]-5-(3,4-diethoxyphenyl)-7-methyl-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-7-methyl-2-[(4-methylsulfanylphenyl)methylidene]-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C28H30N2O5S2
ethyl (2Z,5R)-5-(3,4-diethoxyphenyl)-7-methyl-2-[(4-methylsulfanylphenyl)methylidene]-3-oxo-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— N'-[1-(4-oxocyclohexa-2,5-dien-1-ylidene)ethyl]-2-(2,4,5-trichlorophenoxy)acetohydrazide —— C16H13Cl3N2O3
N'-[1-(4-oxocyclohexa-2,5-dien-1-ylidene)ethyl]-2-(2,4,5-trichlorophenoxy)acetohydrazide
—— (6Z)-6-({3-Chloro-4-[2-(3,4-dimethylphenoxy)ethoxy]-5-ethoxyphenyl}methylidene)-2-ethyl-5-imino-5H,6H,7H-[1,3,4]thiadiazolo[3,2-A]pyrimidin-7-one —— C26H27ClN4O4S
(6Z)-6-({3-Chloro-4-[2-(3,4-dimethylphenoxy)ethoxy]-5-ethoxyphenyl}methylidene)-2-ethyl-5-imino-5H,6H,7H-[1,3,4]thiadiazolo[3,2-A]pyrimidin-7-one
—— (5Z)-5-(3,4-diethoxybenzylidene)-2-(2,6-dimethylmorpholin-4-yl)-1,3-thiazol-4(5H)-one —— C20H26N2O4S
(5Z)-5-(3,4-diethoxybenzylidene)-2-(2,6-dimethylmorpholin-4-yl)-1,3-thiazol-4(5H)-one
—— (6Z)-6-{3-bromo-4-[(4-methylbenzyl)oxy]benzylidene}-5-imino-2-(pyridin-3-yl)-5,6-dihydro-7H-[1,3,4]thiadiazolo[3,2-a]pyrimidin-7-one —— C25H18BrN5O2S
(6Z)-6-{3-bromo-4-[(4-methylbenzyl)oxy]benzylidene}-5-imino-2-(pyridin-3-yl)-5,6-dihydro-7H-[1,3,4]thiadiazolo[3,2-a]pyrimidin-7-one
—— (NZ)-N-[(6E)-1,6-bis(4-ethoxyphenyl)-6-hydroxyiminohexylidene]hydroxylamine —— C22H28N2O4
(NZ)-N-[(6E)-1,6-bis(4-ethoxyphenyl)-6-hydroxyiminohexylidene]hydroxylamine
—— 6-[(5Z)-5-{3-[(4-chlorobenzyl)oxy]benzylidene}-4-oxo-2-thioxo-1,3-thiazolidin-3-yl]hexanoic acid —— C23H22ClNO4S2
6-[(5Z)-5-{3-[(4-chlorobenzyl)oxy]benzylidene}-4-oxo-2-thioxo-1,3-thiazolidin-3-yl]hexanoic acid
—— (2E)-3-{[2-(2-chloro-1,1,2-trifluoroethoxy)phenyl]amino}-2-[4-(3-methoxyphenyl)-1,3-thiazol-2-yl]prop-2-enenitrile —— C21H15ClF3N3O2S
(2E)-3-{[2-(2-chloro-1,1,2-trifluoroethoxy)phenyl]amino}-2-[4-(3-methoxyphenyl)-1,3-thiazol-2-yl]prop-2-enenitrile
—— Ethyl 2-((1H-pyrrol-2-yl)methylene)-5-(4-methoxyphenyl)-7-methyl-3-oxo-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate —— C22H21N3O4S
Ethyl 2-((1H-pyrrol-2-yl)methylene)-5-(4-methoxyphenyl)-7-methyl-3-oxo-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate
—— (6Z)-6-{3-chloro-4-[(3-methylbenzyl)oxy]benzylidene}-5-imino-2-[2-oxo-2-(pyrrolidin-1-yl)ethyl]-5,6-dihydro-7H-[1,3,4]thiadiazolo[3,2-a]pyrimidin-7-one —— C26H24ClN5O3S
(6Z)-6-{3-chloro-4-[(3-methylbenzyl)oxy]benzylidene}-5-imino-2-[2-oxo-2-(pyrrolidin-1-yl)ethyl]-5,6-dihydro-7H-[1,3,4]thiadiazolo[3,2-a]pyrimidin-7-one
—— (2E,5Z)-5-[(4-methoxyphenyl)methylidene]-3-phenyl-2-(1,2,4-triazol-4-ylimino)-1,3-thiazolidin-4-one —— C19H15N5O2S
(2E,5Z)-5-[(4-methoxyphenyl)methylidene]-3-phenyl-2-(1,2,4-triazol-4-ylimino)-1,3-thiazolidin-4-one
—— ethyl (2E,5S)-2-[(3-methoxy-4-phenylmethoxyphenyl)methylidene]-7-methyl-3-oxo-5-thiophen-2-yl-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate —— C29H26N2O5S2
ethyl (2E,5S)-2-[(3-methoxy-4-phenylmethoxyphenyl)methylidene]-7-methyl-3-oxo-5-thiophen-2-yl-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate
—— 1-(3-(diethylamino)propyl)-3-hydroxy-4-(3-methoxybenzoyl)-5-(pyridin-2-yl)-1H-pyrrol-2(5H)-one —— C24H29N3O4
1-(3-(diethylamino)propyl)-3-hydroxy-4-(3-methoxybenzoyl)-5-(pyridin-2-yl)-1H-pyrrol-2(5H)-one
—— 4-methoxy-N-[(Z)-2-(6-methyl-3-propylsulfanyl-1,2,4-triazin-5-yl)ethenyl]aniline —— C16H20N4OS
4-methoxy-N-[(Z)-2-(6-methyl-3-propylsulfanyl-1,2,4-triazin-5-yl)ethenyl]aniline
—— (6Z)-6-({5-Bromo-2-[2-(4-methylphenoxy)ethoxy]phenyl}methylidene)-2-ethyl-5-imino-5H,6H,7H-[1,3,4]thiadiazolo[3,2-A]pyrimidin-7-one —— C23H21BrN4O3S
(6Z)-6-({5-Bromo-2-[2-(4-methylphenoxy)ethoxy]phenyl}methylidene)-2-ethyl-5-imino-5H,6H,7H-[1,3,4]thiadiazolo[3,2-A]pyrimidin-7-one
—— {(2E)-4-oxo-2-[(2Z)-{1-[4-(propan-2-yloxy)phenyl]ethylidene}hydrazinylidene]-1,3-thiazolidin-5-yl}acetic acid —— C16H19N3O4S
{(2E)-4-oxo-2-[(2Z)-{1-[4-(propan-2-yloxy)phenyl]ethylidene}hydrazinylidene]-1,3-thiazolidin-5-yl}acetic acid