Determination of Reactive Hydrogen in Organic Compounds

Abstract

Methods for quantitatively determining reactive hydrogen in organic compounds have been reviewed to find the most suitable procedures for estimating the reactive structural units in coal degradation products. In the past, reaction with methylmagnesium iodide or lithium aluminum hydride has been used to determine total reactive hydrogen in organic compounds with an accuracy o f 1 3 to 5%. The types of compounds which have been determined are: alcohols, phenols, enols, mercaptans, acids. amines, amides, and water. Acylation methods. including acetylation, phthaloylation, benzoylation, ETHODS for quantitatively determiningreactive hydrogen in organic compounds-Le., hydrogen attached tonitrogen. oxygen, or sulfur and exceptionally reactive carbon-hydrogen structures-have been reviewed to find the most suitable procedures for estimating the reactive oxygen-and nitrogen-containing structures in coal degradation products. The chemical literature from 1927 to 1949, inclusive, has been thoroughly searched, and some earlier and more recent references have been consulted The literature previous to 1931 was reviewed by Meyer (93).Methyl Grignard reagents and lithium aluminum hydride will react quantitatively R ith reactive hydrogen atoms in organic compounds t o form methane and hydrogen, respectively. The gaa formed in each case is a memure of the "artive hydrogen." Other reagents have been reported for the determination of active hydrogen but are generally less satisfactory.Some of the active hydrogen atoms can also be replaced b i a(-yl groups, and compounds containing such hydrogen atoms are said to contain "acylatable hydrogen" or usually "acetylatable hydrogrn." ""wylatable hydrogen" and ' acetylatable hydrogen"are not strictly correct t e i m~, inaqmuch as the hydrogen is not acylated but rather replaced by an acyl group. However, these are convenient ternis which distinctly differentiate methods which involve acylation of reactive groups from the methods I T hich determine total "active hydrogen." Different reagents and conditions cause quantitative acylation of different functional groups, and consequently the terms "acylatable hydrogen" and "acetylatahle hydrogen" have little meaning unless the reagent and conditions are specified. Pa 1 Present addreas, Verona Research Center Koppers Co , Inc , Verona,formylation, and stearylation, vary greatly among themselves and give results depending on reagents and conditions. Variations of the most common method-i.e., acetylation using acetic anhydride and pyridine at approximately 100' C.-have been used to determine primary and secondary alcohols, "unhindered" phenols, and primary and secondary amines. Other acylation reagents may be advantageous if tertiary alcohols or pyrroles must be determined or selectivity of reaction is desired. Applicability of different acylation methods for determining functional groups has been tabulated.The methods of deterniining reactive hydrogen have thus been divided into two major groups-determinations of active hydrogrn and determinations o...

Methylmagnesium Chloride as Reagent for Determination of Reactive Hydrogen

“…Because many organic compounds containing active hydrogen are insoluble in the solvent ordinarily used for the preparation of the Grignard reagent (pentyl ether), a number of secondary solvents have been required (3). Use of these additional solvents requires exacting purification and necessitates blank determinations for precise results.…”

“…A study of the quinalizarin test (3,4) revealed that when the volume of the test solution is increased to 1 ml. (instead of the recommended few drops) the quantity of base and/or salts present, as well as the degree of drying, becomes critical.…”

Volumetric Analytical Methods for Organic Compounds

“…The procedures for the determination of reactive hydrogen have been reviewed (117) for possible application in the estimation of reactive structural units in coal degradation products.…”

Essential Oils and Related Products

“…Schoniger (128) used the apparatus of Soltys for a microdetermination of double bonds. Olleman (102) published an excellent review of the methods employed for the determination of reactive hydrogen in organic compounds. The second part of this paper discussed methods for acylation (particularly acetylation) of certain compounds; the difficulties encountered with tertiary alcohols are stressed.…”