ASTM E222-2010 6875 Standard Test Methods for Hydroxyl Groups Using Acetic Anhydride Acetylation《乙酸酐乙酰化法进行羟基试验的标准试验方法》.pdf

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1、Designation: E222 10Standard Test Methods forHydroxyl Groups Using Acetic Anhydride Acetylation1This standard is issued under the fixed designation E222; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A

2、number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 These test methods cover the determination of hydroxylgroups attached to primary and secondary carbon atoms inaliphatic and alicyclic

3、compounds and phenols.1.2 Three test methods are given as follows:SectionsTest Method A (Pressure Bottle Method) 8-14Test Method B (Reflux Method) 15-21Test Method C (Perchloric Acid Catalyzed Method) 22-281.2.1 Test Method A is recommended for general use. TestMethod B is included to give a standar

4、d procedure for themethod that has been used widely. Test Method C is recom-mended when the results are required in a minimum period oftime or where ambient temperature for the reaction is desired.1.2.2 The results obtained using Test Methods A and B willbe essentially the same, but the results obta

5、ined using TestMethod C will be higher (up to approximately 4 % relative)than those obtained using the other two methods.1.2.3 Statements on precision are included with each testmethod. The precision of Test Methods A and C is consistentover a wide range of hydroxyl content (tested over hydroxylnumb

6、er range of 250 to 1600), whereas Test Method B is lessprecise at the higher hydroxyl content level than it is at thelower hydroxyl content level. In general, Test Method A isapproximately two-fold as precise as Test Method C. TestMethod B has approximately the same precision as TestMethod C at the

7、lower hydroxyl content level but poorerprecision at the higher hydroxyl content level.1.2.4 The interferences are essentially the same for the threemethods. Some compounds can be analyzed using Test Meth-ods A or B but not using Test Method C because of interferingreactions of the strong acid cataly

8、st with the compound beinganalyzed or the acetate product formed in the determination.However, because of its increased reactivity, Test Method C isapplicable for determination of some compounds, particularlysterically hindered secondary alcohols, which react too slowlyor not at all in Test Methods

9、A and B.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 Review the current appropriate Material Safety DataSheets (MSDS) for detailed information concerning toxicity,first aid procedures, and safety precautions.1.5 This

10、standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Specific hazardsstateme

11、nts are given in Section 7.NOTE 1Other methods for determination of hydroxyl groups aregiven in Test Methods D1957, D2195, E326, E335, and E567.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD1957 Test Method for Hydroxyl Value of Fatty Oils andAcids3D2195 Test Metho

12、ds for PentaerythritolE180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals3E200 Practice for Preparation, Standardization, and Storageof Standard and Reagent Solutions for Chemical AnalysisE203 Test Method for Water Using Volumetr

13、ic Karl FischerTitrationE326 Test Method for Hydroxyl Groups by Phthalic Anhy-dride Esterification (Discontinued 2001)3E335 Test Method for Hydroxyl Groups by PyromelliticDianhydride Esterification3E567 Test Method for Tertiary Hydroxyl Groups withHydrogen Bromide3. Terminology3.1 Definition:1These

14、test methods are under the jurisdiction of ASTM Committee E15 onIndustrial and Specialty Chemicals and are the direct responsibility of Subcommit-tee E15.01 on General Standards.Current edition approved March 1, 2010. Published April 2010. Originallyapproved in 1963. Last previous edition approved i

15、n 2005 as E222 00(05)1. DOI:10.1520/E0222-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The

16、last approved version of this historical standard is referencedon www.astm.org.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.1 hydroxyl numberthe milligrams of p

17、otassium hy-droxide equivalent to the hydroxyl content of1gofmaterial.In the case of a pure compound, the hydroxyl number isinversely proportional to the hydroxyl equivalent weight:equivalent weight g/equivalent!556100hydroxyl number(1).4. Significance and Use4.1 Hydroxyl is an important functional

18、group, and knowl-edge of its content is required in many intermediate and enduse applications. The test methods described herein are for thedetermination of primary and secondary hydroxyl groups andcan be used for the assay of compounds containing them.5. Interferences5.1 Unless stated otherwise, th

19、e following interferencesapply to all three test methods:5.1.1 Pentavalent nitrogen compounds, amides, someethers, and some carbonyl compounds may interfere with theaccuracy of the test method.5.1.2 Tertiary alcohols, cyanohydrins, some hydroxylatedfatty acids, certain substituted phenols, and some

20、polyhydroxylcompounds will react in a nonstoichiometric manner.5.1.3 Primary and secondary amines and mercaptans usu-ally will react quantitatively along with the hydroxyl group.5.1.4 Excessive amounts of water in the sample will inter-fere by consuming the reagent. Provisions are made to accom-moda

21、te a small amount of water by adjustment of the samplesize used for the analysis.5.1.5 Free acids interfere by consuming the standard alkalisolution, and strong bases interfere by consuming an equiva-lent amount of acetic acid; provisions for determining andapplying corrections for these interferenc

22、es are included in thetest methods. Some of the higher fatty acids may be convertedto anhydrides, releasing water which will consume acetylationreagent.5.1.6 In Test Method C, epoxy, poly(oxyethylene), poly(ox-ypropylene), and furan rings interfere. Enols, imides, hy-drazides, and some oximes will r

23、eact in a nonstoichiometricmanner.5.1.7 Phenol (in contrast to other phenolics) gives lowresults with Test Methods A and B.5.1.8 With Test Methods A and B, epoxy compounds willgive erroneously high results.NOTE 2In a study performed by the American Oil Chemists Society,satisfactory results were obta

24、ined with epoxidized soybean oil, epoxidizedtall oil, and epoxidized castor oil when the acetylation was carried out atroom temperature for 24 h.5.1.9 Presence of an olefinic or acetylenic unsaturation inthe hydroxyl-containing compound should have no effect onthe hydroxyl content result obtained wi

25、th Test Methods A andB, but may give a positive interference with Test Method C.5.1.10 Test Methods A and B as written (using a visualindicator) may not be applicable to samples containing heat-sensitive impurities, leading to high color in the reactedsolution.6. Reagents6.1 Purity of ReagentsReagen

26、t grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.4Other grades may beused, provided it is firs

27、t ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.6.2 Unless otherwise indicated, references to water shall beunderstood to mean Type II or Type III reagent water conform-ing to Specification D1193.7. Hazards7.1 Acetic a

28、nhydride, pyridine, and 1,2-dichloroethane areeye, skin, and respiratory irritants. Avoid bodily contact withthese reagents and use only in a well-ventilated area.7.2 Perchloric acid is commonly available in 60 to 72 %concentrations. These solutions may form explosive mixtureswith certain organic ma

29、terials. Dehydrating agents may causethe formation of the anhydrous acid which is unstable atambient temperature and explodes on contact with mostorganic materials. The acid is an acute irritant to the eyes, skin,and mucous membranes. Avoid bodily contact. Wash all spillswith copious amounts of wate

30、r.TEST METHOD A(Pressure Bottle Method)8. Summary of Test Method8.1 The sample is acetylated with a solution of aceticanhydride in pyridine in a pressure bottle at 98C. The excessreagent is hydrolyzed with water, and the acetic acid is titratedwith standard sodium hydroxide solution. The hydroxyl co

31、n-tent is calculated from the difference in titration of the blankand sample solutions.9. Apparatus9.1 Bag, heavy fabric, with draw string, to hold bottle (9.2).As an alternative a stainless steel mesh jacket fitted to cover thebottle may be used.9.2 Bottle, pressure, heat-resistant, approximately 3

32、50 mL.9.3 Buret, 100-mL total capacity, range of graduated portion50 mL, 0.1-mL graduations, preferably equipped with PTFEstopcock (see Note 6).9.4 Steam Bath,986 2C, containing enough water tocover the liquid in the sample bottles. It is critical that the waterlevel be as prescribed and that the te

33、mperature be within theprescribed range and uniform throughout the bath.10. Reagents10.1 Acetic Anhydride.(Caution: see 7.1)4Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Ch

34、emical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.E222 10210.2 Acetylation ReagentMix 127 mL of acetic anhydridewith 1000 mLof pyridine (10.5)

35、. The reagent shall be preparedfresh daily and kept in a dark bottle. It should not be used ifdarker than a pale yellow color.10.3 Hydrochloric Acid, Standard Solution (0.5 meq/mL)Prepare and standardize in accordance with the appropriatesections of Practice E200. Determine and record the tempera-tu

36、re at which the standardization was performed. The concen-tration of the solution shall be corrected to the temperature atwhich the determination is performed as described in 10.6. Thefactor for the thermal expansion of this solution is 0.00014.This solution is required only if a correction is to be

37、 applied forthe presence of strong base in the sample being analyzed.10.4 Phenolphthalein Indicator SolutionDissolve1gofphenolphthalein in 100 mL of pyridine.10.5 Pyridine, containing 0.30 to 0.45 % water. Determinethe water content of the pyridine using Test Method E203, andadd the required amount

38、of water. The volume of water to addper litre of pyridine may be calculated as follows:Water to add, mL 5 4.0 2 9A (2)where:A = percent water in pyridine.10.6 Sodium Hydroxide, Standard Solution (0.5 meq/mL)(Caution: See 7.1)Prepare and standardize in accordancewith the appropriate sections of Pract

39、ice E200. Determine andrecord the temperature at which the standardization wasperformed. The factor for thermal expansion of this solution is0.00014. For calculation of the hydroxyl content, the normalityof the solution shall be corrected to the temperature at whichthe determination is performed by

40、the following:Nt25 Nt11 t12 t2! F! (3)where:Nt1= meq/mL when standardized,Nt2= meq/mL during analysis of samples,t1= temperature of solution (C) during standardization,t2= temperature of solution (C) during analysis ofsamples, andF = factor to correct for thermal expansion of thesolution (see each s

41、olution for appropriate factor).11. Procedure11.1 To each of a sufficient number of pressure bottles tomake all blank and sample determinations in duplicate, pipet20.0 mL of the acetylation reagent. A uniform drainage timemust be used for all aliquots.11.2 Reserve two of the bottles for the blank de

42、termination.Into the other bottles introduce an appropriate weight of sample(Note 3, Note 4, and Note 7).NOTE 3The sample size is based on a maximum of 9.8 meq ofhydroxyl being present. Determine the sample weight using one of thefollowing equations:Sample weight, g 5 561 3 0.98!/approximate hydroxy

43、l number(4)Sample weight, g 5 0.0098 3 MW/n (5)where:MW = molecular weight of the hydroxyl-containing compound, andn = number of hydroxyl groups present in the molecule.Since the calculated sample weight will be near the maximum permittedby the test method, adhere closely to the indicated weight. Th

44、e sampleshould not exceed 10 g.NOTE 4If the sample contains an appreciable amount of water, thesample weight must be adjusted to accommodate this interference. In thiscase, determine the sample weight using one of the following equations:Sample weight, g 50.1701 3 0.980.0094R 1 0.01S 3 n 3 17.01!/MW

45、(6)Sample weight, g 5550approximate hydroxyl number 131.2 3 R!(7)where:R = water in the sample, %,S = purity of the sample, %,MW = molecular weight of the hydroxyl-containing compound, andn = number of hydroxyl groups present in the molecule.Precision and accuracy are decreased when appreciable amou

46、nts of waterare present because of the required decrease in sample size.11.3 Stopper the bottle and swirl until the sample is com-pletely dissolved. Enclose each bottle in a fabric bag and placeall bottles as close together as possible in the steam bath at 986 2Cfor2h(Note 5). Maintain sufficient wa

47、ter in the bath tocover the level of liquid in the bottles.NOTE 5A reaction time of2hissatisfactory for most primaryalcohols. Secondary alcohols react more slowly, and a general reactiontime of4hisrecommended. For some compounds a shorter or a longerreaction period may be required.11.4 Remove the bo

48、ttles from the bath and allow them tocool to room temperature. Untie the bags, uncap the bottles torelease any pressure, and then remove the bags.11.5 Carefully rinse any liquid on the stopper into the bottleand rinse the walls of the flask, using 20 to 30 mL of water. Toeach of the bottles add clea

49、n crushed ice until about one halffull.11.6 Add 1 mL of the phenolphthalein indicator solutionand titrate (Note 6) immediately with the 0.5 meq/mL NaOHsolution to the first faint pink end point permanent for 15 s. Thesolution should be swirled during the titration, with vigorousswirling as the end point is reached. Record the volume oftitrant to 0.02 mL (Note 7). Record the temperature of theNaOH solution.NOTE 6As a substitute, if the 100-mL buret is not available, the first50 mL of titrant may be added by pipet (uniform drainage time for allaliquots) and