| Revision as of 04:37, 13 June 2011 editCheMoBot (talk | contribs)Bots141,565 edits Updating {{chembox}} (changes to verified and watched fields - added verified revid - updated 'UNII_Ref', 'ChemSpiderID_Ref', 'StdInChI_Ref', 'StdInChIKey_Ref', 'ChEMBL_Ref') per [[Misplaced Pages:WikiProject Chemicals/Chembox validation|Chem/Drugbox valid← Previous edit |
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{{short description|Chemical indicator that turns red in acidic solutions}} |
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{{Chembox |
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{{Chembox |
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| Verifiedfields = changed |
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| Watchedfields = changed |
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| Watchedfields = changed |
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| verifiedrevid = 386417462 |
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| verifiedrevid = 433999215 |
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| Name = Methyl red |
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| Name = Methyl red |
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| ImageFile1 = Methyl red.svg |
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| ImageFile1 = Methyl red.svg |
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| ImageSize1 = 240px |
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| ImageSize1 = |
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| ImageName1 = Skeletal formula of methyl red |
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| ImageName1 = Skeletal formula of methyl red |
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| ImageFile2 = Methyl-red-from-xtal-3D-balls.png |
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| ImageFile2 = Methyl-red-from-xtal-3D-balls.png |
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| ImageSize2 = 240px |
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| ImageSize2 = |
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| ImageName2 = Ball-and-stick model of methyl red |
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| ImageName2 = Ball-and-stick model of methyl red |
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| ImageFile3 = Crystals of Methyl red sodium salt.jpg |
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| Section1 = {{Chembox Identifiers |
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| ImageSize3 = |
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| CASNo_Ref = {{cascite}} |
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| PIN = 2-<nowiki/>{diazenyl}<br />benzoic acid |
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|Section1={{Chembox Identifiers |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| CASNo = 493-52-7 |
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| CASNo = 493-52-7 |
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| CASNo_Comment = (free base) |
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| CASOther = <br /> <small>(HCl salt)</small>,<br /><small> (sodium salt)</small> |
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| KEGG_Ref = {{keggcite|changed|kegg}} |
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| CASNo1_Ref = {{cascite|correct|CAS}} |
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| CASNo1 = 63451-28-5 |
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| CASNo1_Comment = (HCl salt) |
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| CASNo2_Ref = {{cascite|correct|CAS}} |
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| CASNo2 = 845-10-3 |
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| CASNo2_Comment = (sodium salt) |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| UNII = 69083AX1ZX |
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| UNII_Comment = (free base) |
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| UNII1_Ref = {{fdacite|correct|FDA}} |
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| UNII1 = RFA0W63690 |
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| UNII1_Comment = (HCl salt) |
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| UNII2 = 311GZ0QHWN |
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| UNII2_Comment = (sodium salt) |
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| UNII2_Ref = {{fdacite|correct|FDA}} |
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| ChEBI_Ref = {{ebicite|correct|EBI}} |
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| ChEBI = 49770 |
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| EINECS = 207-776-1 |
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| KEGG_Ref = {{keggcite|correct|kegg}} |
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| KEGG = C19459 |
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| KEGG = C19459 |
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| SMILES = CN(C)c2ccc(/N=N/<br />c1ccccc1C(O)=O)cc2 |
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| SMILES = CN(C)c2ccc(/N=N/c1ccccc1C(O)=O)cc2 |
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| PubChem = 10303 |
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}} |
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| RTECS = DG8960000 |
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| Section2 = {{Chembox Properties |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| C=15 | H=15 | N=3 | O =2 |
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| ChemSpiderID = 9881 |
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| Density = 0.791 g/cm<sup>3</sup> |
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| InChI = 1/C15H15N3O2/c1-18(2)12-9-7-11(8-10-12)16-17-14-6-4-3-5-13(14)15(19)20/h3-10H,1-2H3,(H,19,20)/b17-16+ |
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| MeltingPt = 179-182 °C, 452-455 K |
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| InChIKey = CEQFOVLGLXCDCX-WUKNDPDIBD |
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| BoilingPt = |
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| StdInChI_Ref = {{stdinchicite|changed|chemspider}} |
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}} |
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| StdInChI = 1S/C15H15N3O2/c1-18(2)12-9-7-11(8-10-12)16-17-14-6-4-3-5-13(14)15(19)20/h3-10H,1-2H3,(H,19,20)/b17-16+ |
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| Section7 = {{Chembox Hazards |
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| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}} |
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| RPhrases = {{R20}} {{R21}} {{R22}} {{R36}} {{R37}} {{R38}} {{R40}} |
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| StdInChIKey = CEQFOVLGLXCDCX-WUKNDPDISA-N |
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}} |
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}} |
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|Section2={{Chembox Properties |
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| C=15 | H=15 | N=3 | O=2 |
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| Density = 0.791 g/cm<sup>3</sup> |
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| MeltingPtC = 179-182 |
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| MeltingPt_ref = <ref name=sigma /> |
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| BoilingPt = |
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| LambdaMax = 410 nm (yellow form)<ref name=sigma>], {{Webarchive|url=https://web.archive.org/web/20151209184611/http://www.sigmaaldrich.com/catalog/product/sial/250198 |date=2015-12-09 }}. Retrieved on 2014-06-02.</ref> |
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| SolubleOther = soluble in ethanol<ref name=sigma /> |
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| pKa = 5.1 |
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}} |
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|Section7={{Chembox Hazards |
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| GHSPictograms = {{GHS08}}{{GHS09}} |
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| GHSSignalWord = Warning |
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| HPhrases = {{H-phrases|351|411}} |
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| PPhrases = {{P-phrases|201|202|273|281|308+313|391|405|501}} |
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| NFPA-H = 2 |
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| NFPA-F = 1 |
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| NFPA-R = 0 |
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}} |
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}} |
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}} |
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{{pH_indicator_template|indicator_name=Methyl Red|low_pH=4.4|high_pH=6.2|low_pH_color=red|high_pH_color=yellow}} |
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{{pH_indicator_template|indicator_name=Methyl Red|low_pH=4.4|high_pH=6.2|low_pH_color=red|high_pH_color=yellow|low_pH_text=white}} |
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'''Methyl red''' (2-(''N'',''N''-dimethyl-4-aminophenyl) azobenzenecarboxylic acid), also called '''C.I. Acid Red 2''', is an ] dye that turns red in ]ic solutions. It is an ], and is a dark red crystalline powder. Methyl red is a ]; it is red in pH under 4.4, yellow in pH over 6.2, and orange in between, with a ] of 5.1.<ref>IB chemistry Higher Level: {{cite web |url=https://ibchem.com/IB/ibnotes/full/aab_htm/18.6.htm |title=IB Chemistry higher level notes: Indicators |access-date=2009-11-29 |url-status=dead |archive-url=https://web.archive.org/web/20090922042431/https://ibchem.com/IB/ibnotes/full/aab_htm/18.6.htm |archive-date=2009-09-22 }}</ref> ] and methyl red are investigated as promising enhancers of ] destruction of ] ]s. Methyl red is classed by the ] in ] - unclassified as to ] potential in humans. |
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] |
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==Preparation== |
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'''Methyl red''', also called '''C.I. Acid Red 2''', is an ] dye that turns red in ]ic solutions. It is an ], and is a dark red crystalline powder. |
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As an azo dye, methyl red may be prepared by ] of ], followed by reaction with ]:<ref>{{OrgSynth | author = H. T. Clarke |author2=W. R. Kirner |name-list-style=amp | title = Methyl Red | collvol = 1 | collvolpages = 374 | prep = cv1p0374 | year = 1941}}</ref> |
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==Properties== |
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Methyl red is a ]; it is red in pH under 4.4, yellow in pH over 6.2, and orange in between, with a ] of 5.1 <ref>IB chemistry Higher Level: http://ibchem.com/IB/ibnotes/full/aab_htm/18.6.htm</ref>. |
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The color of methyl red is pH dependent, because protonation causes it to adopt a ]/] structure. |
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Methyl Red has a special use in histopathology for showing acidic nature of tissue and presence of organisms with acidic natured cell walls. |
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] and methyl red are investigated as promising enhancers of ] destruction of ] ]s.<ref name="cs.odu.edu">{{Dead link|date=March 2008}}</ref> |
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Methyl Red is detectably fluorescent in 1:1 water:methanol (pH 7.0), with an emission maximum at 375 nm (]) upon excitation with 310 nm light (]).<ref name="Kumar Das Goswami Barman Das pp. 75–78">{{cite journal | last1=Kumar Das | first1=Diganta | last2=Goswami | first2=Priyanka | last3=Barman | first3=Champa | last4=Das | first4=Biva | title=Methyl Red: A Fluorescent Sensor for Hg2+ over Na+, K+, Ca2+, Mg2+, Zn2+, and Cd2+ | journal=Environmental Engineering Research | publisher=Korean Society of Environmental Engineering | date=2012-12-30 | issn=1226-1025 | doi=10.4491/eer.2012.17.s1.s75 | pages=75–78}}</ref> |
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Methyl red is classed by the ] in ] - unclassified as to ] potential in humans. |
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==Preparation== |
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As an azo dye, Methyl Red may be prepared by ] of ], followed by reaction with ]:<ref>{{OrgSynth | author = H. T. Clarke and W. R. Kirner | title = Methyl Red | collvol = 1 | collvolpages = 374 | prep = cv1p0374 | year = 1941}}</ref> |
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==Methyl red test== |
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==Methyl red test== |
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]'' (left side) showing a 'positive' result, and '']'' (right side) showing a 'negative' result]] |
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In ], methyl red is used in the ], used to identify ] producing stable acids by mechanisms of mixed acid ] of ] (''cf.'' ] (VP) test). |
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In ], methyl red is used in the methyl red test (MR test), used to identify ] producing stable acids by mechanisms of mixed acid ] of ] (''cf.'' ] test). |
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The methyl red test is the "M" portion of the four IMViC tests used to characterize enteric bacteria. The methyl red test is used to identify enteric bacteria based on their pattern of glucose metabolism. All enterics initially produce pyruvic acid from glucose metabolism. Some enteric subsequently use the mixed acid pathway to metabolize pyruvic acid to other acids, such as lactic, acetic, and formic acids. These bacteria are called methyl-red positive and include ''Escherichia coli'' and ''Proteus vulgaris''. Other enterics subsequently use the buytylene glycol pathway to metabolize pyruvic acid to neutral end-products. These bacteria are called methyl-red-negative and include ''Serratia marcescens'' and ''Enterobacter aerogenes''.<ref name="cs.odu.edu"/> |
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The MR test, the "M" portion of the four ] tests, is used to identify enteric bacteria based on their pattern of glucose metabolism. All enterics initially produce ] from glucose metabolism. Some enterics subsequently use the mixed acid pathway to metabolize pyruvic acid to other acids, such as ], ], and ] acids. These bacteria are called methyl-red positive and include '']'' and '']''. Other enterics subsequently use the ] pathway to metabolize pyruvic acid to neutral end products. These bacteria are called methyl-red-negative and include '']'' and '']''. |
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===Process=== |
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===Process=== |
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An isolate is inoculated into a tube with a sterile transfer loop. The tube is incubated at 35°C for 2-5 days. After incubation, 2.5ml of the medium is transferred to another tube. Five drops of the pH indicator methyl red is added to this tube. The tube is gently rolled between the palms of the hands to disperse the methyl red.<ref name="cs.odu.edu"/> |
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A tube filled with a ] is inoculated with a sterile transfer loop. The tube is incubated at {{convert|35|C}} for 2–5 days. After incubation, 2.5 ml of the medium are transferred to another tube. Five drops of the pH indicator methyl red is added to this tube. The tube is gently rolled between the palms to disperse the methyl red. |
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===Expected results=== |
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===Expected results=== |
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Enterics that subsequently metabolize pyruvic acid to other acids lower the pH of the medium to 4.2. At this pH, methyl red turns red. A red color represents a positive test. Enterics that subsequently metabolize pyruvic acid to neutral end-products lower the pH of the medium to only 6.0. At this pH, methyl red is yellow. A yellow color represents a negative test.<ref name="cs.odu.edu"/> |
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Enterics that subsequently metabolize pyruvic acid to other acids lower the pH of the medium to 4.2. At this pH, methyl red turns red, a positive test. Enterics that subsequently metabolize pyruvic acid to neutral end products lower the pH of the medium to only 6.0. At this pH, methyl red is yellow, a negative test. |
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==See also== |
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==See also== |
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== External links == |
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== External links == |
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{{Commons category|Methyl red}} |
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* A site showing some extra information on methyl red. |
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* A site showing some extra information on methyl red. |
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{{Clinical microbiology techniques}} |
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