ASTM E222-17 Standard Test Methods for Hydroxyl Groups Using Acetic Anhydride Acetylation.pdf

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1、Designation: E222 17Standard 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) 814Test Method B (Reflux Method) 1622Test Method C (Perchloric Acid Catalyzed Method) 24301.2.1 Test Method A is recommended for general use. TestMethod B is included to give a standard p

4、rocedure 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 obtaine

5、d 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 hydroxylnumber

6、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 low

7、er 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 catalyst

8、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 A a

9、nd B.NOTE 1Other methods for determination of hydroxyl groups are givenin Test Methods D1957, D2195, E326, E335, and E567.1.3 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 Safety Data Sheets(

10、SDS) for detailed information concerning toxicity, first aidprocedures, and safety precautions.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 pr

11、actices and determine the applica-bility of regulatory limitations prior to use. Specific hazardsstatements are given in Section 7.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for

12、 theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD1957 Test Method for Hydroxyl Value of Fatty Oils andAcids (Withd

13、rawn 2007)3D2195 Test Methods for Pentaerythritol (Withdrawn 2011)3D6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemical

14、s (Withdrawn 2009)3E200 Practice for Preparation, Standardization, and Storageof Standard and Reagent Solutions for Chemical AnalysisE203 Test Method for Water Using Volumetric Karl FischerTitration1These test methods are under the jurisdiction of ASTM Committee D16 onAromatic, Industrial, Specialty

15、 and Related Chemicals and are the direct responsi-bility of Subcommittee D16.15 on Industrial and Specialty General Standards.Current edition approved June 1, 2017. Published July 2017. Originally approvedin 1963. Last previous edition approved in 2010 as E222 10. DOI: 10.1520/E0222-17.2For referen

16、ced 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.3The last approved version of this historical standard is referenced onww

17、w.astm.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardi

18、zation established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1E326 Test Method for Hydroxyl Groups by Phthalic Anhy-dride Esterification (Withdrawn 2001)3E

19、335 Test Method for Hydroxyl Groups by PyromelliticDianhydride Esterification (Withdrawn 2002)3E567 Test Method for Tertiary Hydroxyl Groups with Hy-drogen Bromide (Withdrawn 1996)33. Terminology3.1 Definitions:3.1.1 hydroxyl numberthe milligrams of potassium hy-droxide equivalent to the hydroxyl co

20、ntent 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 group, and knowl-edge of its content is required

21、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, the following interferencesapply to all three test

22、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 polyhydroxylcompounds will react in a nonstoichio

23、metric 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-modate a small amount of water by adjustment of the s

24、amplesize 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 interferences are included in thetest methods. Some of the h

25、igher fatty acids may be convertedto anhydrides, releasing water which will consume acetylationreagent.5.1.6 In Test Method C, epoxy, poly(oxyethylene),poly(oxypropylene), and furan rings interfere. Enols, imides,hydrazides, and some oximes will react in a nonstoichiometricmanner.5.1.7 Phenol (in co

26、ntrast 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 obtained with epoxidized soybean oil, epoxidizedtall oil,

27、 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 with Test Methods A andB, but may give a positive inter

28、ference 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 ReagentsReagent grade chemicals shall beused in all tests. Unless o

29、therwise 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 first ascertained that the reagent is ofsufficiently high

30、 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 anhydride, pyridine, and 1,2-dichloroethane areeye, sk

31、in, 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 materials. Dehydrating agents may causethe formation of

32、 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 water.TEST METHOD A(Pressure Bottle Method)8. Summary of

33、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 con-tent is calculated from the difference in titration

34、 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 350 mL.4Reagent Chemicals, American Chemical Society S

35、pecifications, AmericanChemical Society, 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 Co

36、nvention, Inc. (USPC), Rockville,MD.E222 1729.3 Buret, 100-mLtotal capacity, range of graduated portion50 mL, 0.1-mL graduations, preferably equipped with PTFEstopcock (see Note 6).9.4 Steam Bath, 98 6 2C, containing enough water tocover the liquid in the sample bottles. It is critical that the wate

37、rlevel 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.)10.2 Acetylation ReagentMix 127 mL of acetic anhydridewith 1000 mLof pyridine (10.5). The reagent shall be preparedfresh daily and kept

38、 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-ture at which the standardization was performed. The

39、concen-tration of the solution shall be corrected to the temperature atwhich the determination is performed as described in Note 8.10.4 The factor for the thermal expansion of this solution is0.00014. This solution is required only if a correction is to beapplied for the presence of strong base in t

40、he sample beinganalyzed.10.5 Phenolphthalein Indicator SolutionDissolve1gofphenolphthalein in 100 mL of pyridine.10.6 Pyridine, containing 0.30 to 0.45 % water. Determinethe water content of the pyridine using Test Method E203, andadd the required amount of water. The volume of water to addper litre

41、 of pyridine may be calculated as follows:Water to add, mL 5 4.0 2 9A (2)where:A = percent water in pyridine.10.7 Sodium Hydroxide, Standard Solution (0.5 meq/mL)(Caution: See 7.1)Prepare and standardize in accordancewith the appropriate sections of Practice E200. Determine andrecord the temperature

42、 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 Nt11t12 t2!F! (3)where:Nt1

43、= 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 the solution(see each solution for appropriate factor).11. Procedure11

44、.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 introduce an

45、 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 30.98!/approximate hydroxyl number (4)Sample weight, g 5 0.0098 3MW/n (5)w

46、here: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 maximumpermitted by the test method, adhere closely to the indicated weight. Thesample should not exceed 10 g.NOTE 4If the samp

47、le 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 30.980.0094R10.01S 3 n 317.01!/MW#(6)Sample weight, g 5550approximate hydroxyl number

48、131.2 3R!(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 ofwater are present because of the required decre

49、ase 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 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 bottles