ASTM E222-2000(2005)e1 Standard Test Methods for Hydroxyl Groups Using Acetic Anhydride Acetylation《用乙酸酐乙酰化测定羟基团的标准试验方法》.pdf

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1、Designation: E 222 00 (Reapproved 2005)e1Standard Test Methods forHydroxyl Groups Using Acetic Anhydride Acetylation1This standard is issued under the fixed designation E 222; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea

2、r of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEEditorial changes were made in March 2005.1. Scope1.1 These test methods cover the determination of hydroxylgroups att

3、ached to primary and secondary carbon atoms inaliphatic and alicyclic 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 r

4、ecommended for general use. TestMethod B is included to give a standard 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

5、Test Methods A and B willbe essentially the same, but the results obtained 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 con

6、sistentover a wide range of hydroxyl content (tested over hydroxylnumber 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. Tes

7、tMethod B has approximately the same precision as TestMethod C at the 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 T

8、est Method C because of interferingreactions of the strong acid catalyst 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 se

9、condary alcohols, which react too slowlyor not at all in Test Methods A and B.1.3 The values stated in SI units are to be regarded as thestandard.1.4 Review the current appropriate Material Safety DataSheets (MSDS) for detailed information concerning toxicity,first aid procedures, and safety precaut

10、ions.1.5 This 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

11、hazardsstatements are given in Section 7.NOTE 1Other methods for determination of hydroxyl groups aregiven in Test Methods D 1957, D 2195, E 326, E 335, and E 567.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterD 1957 Test Method for Hydroxyl Value of Fatty Oils andA

12、cidsD 2195 Test Methods for PentaerythritolE 180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial ChemicalsE 200 Practice for Preparation, Standardization, and Stor-age of Standard and Reagent Solutions for ChemicalAnalysisE 203 Test Method for Water Using

13、 Karl Fischer ReagentE 326 Test Method for Hydroxyl Groups by Phthalic Anhy-dride EsterificationE 335 Test Method for Hydroxyl Groups by PyromelliticDianhydride EsterificationE 567 Test Method for Tertiary Hydroxyl Groups withHydrogen Bromide3. Terminology3.1 Definition:3.1.1 hydroxyl numberthe mill

14、igrams of potassium hy-droxide equivalent to the hydroxyl content of1gofmaterial.1These 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 StandardsCurrent edition approved March 1, 2

15、005. Published April 2005. Originallyapproved in 1963. Last previous edition approved in 2000 as E 222 00.2For 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 standa

16、rds Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.In the case of a pure compound, the hydroxyl number isinversely proportional to the hydroxyl equivalent weight:equivalent weight g/equivalen

17、t!556100hydroxyl number(1).4. Significance and Use4.1 Hydroxyl is an important functional 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

18、for the assay of compounds containing them.5. Interferences5.1 Unless stated otherwise, the 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 al

19、cohols, cyanohydrins, some hydroxylatedfatty acids, certain substituted phenols, and some 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

20、 in the sample will inter-fere by consuming the reagent. Provisions are made to accom-modate 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 amoun

21、t of acetic acid; provisions for determining andapplying corrections for these interferences 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-

22、ypropylene), and furan rings interfere. Enols, imides, hy-drazides, and some oximes will react 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

23、 2In a study performed by the American Oil Chemists Society,satisfactory results were obtained 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 hy

24、droxyl-containing compound should have no effect onthe hydroxyl content result obtained with 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 impuri

25、ties, leading to high color in the reactedsolution.6. Reagents6.1 Purity of ReagentsReagent 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 Soc

26、iety,where such specifications are available.3Other grades may beused, provided it is first 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 T

27、ype II or Type III reagent water conform-ing to Specification D 1193.7. Hazards7.1 Acetic anhydride, 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 6

28、0 to 72 %concentrations. These solutions may form explosive mixtureswith certain organic materials. 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, s

29、kin,and mucous membranes. Avoid bodily contact. Wash all spillswith copious amounts of water.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 wat

30、er, and the acetic acid is titratedwith standard sodium hydroxide solution. The hydroxyl con-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

31、fitted to cover thebottle may be used.9.2 Bottle, pressure, heat-resistant, approximately 350 mL.49.3 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 liqui

32、d in the sample bottles. It is critical that the waterlevel be as prescribed and that the temperature be within theprescribed range and uniform throughout the bath.10. Reagents10.1 Acetic Anhydride.(Caution: see 7.1)3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Socie

33、ty, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical 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.4

34、A suitable bottle is available from B. Preiser Co. Inc., Catalog No. 10-5485,Chemical Rubber Co., Catalog No. 33052A; and Scientific Glass Co., Catalog No.B5317.E 222 00 (2005)e1210.2 Acetylation ReagentMix 127 mL of acetic anhydridewith 1000 mLof pyridine (10.5). The reagent shall be preparedfresh

35、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 N)Prepare and standardize in accordance with the appropriatesections of Practice E 200. Determine and record the tempera-ture at which the standardization was perfo

36、rmed. 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 applied forthe presence of strong base i

37、n 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 E 203, andadd the required amount of water. The volume of water to addper

38、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 N)(Caution: See 7.1)Prepare and standardize in accordancewith the appropriate sections of Practice E 200. Determine andrecord the temperatur

39、e 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 the following:Nt25 Nt11 t12 t2! F! (3)where:

40、Nt1= normality when standardized,Nt2= normality 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 solution for appropriate factor).11. Pr

41、ocedure11.1 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 determination.Into the other bottles int

42、roduce 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 hydroxyl number(4)Sample weight, g 5 0.0098 3

43、 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. The sampleshould not exceed 10 g.NOTE 4I

44、f 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(6)Sample weight, g 5550approximate hy

45、droxyl 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 amounts of waterare present because of the

46、 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 water in the bath tocover the level of l

47、iquid 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 bottles from the bath and allow them toc

48、ool 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 clean crushed ice until about one halffull

49、.11.6 Add 1 mL of the phenolphthalein indicator solutionand titrate (Note 6) immediately with the 0.5 N NaOH solutionto the first faint pink end point permanent for 15 s. The solutionshould be swirled during the titration, with vigorous swirling asthe end point is reached. Record the volume of titrant to 0.02mL (Note 7). Record the temperature of the NaOH 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 the titration completed with a 50-mL buret.