Determination of Active Hydrogen Using Grignard Reagent in Pyridine

Lehman, Robert A.; Basch, H.

doi:10.1021/i560143a008

Cited by 8 publications

(2 citation statements)

References 8 publications

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“…For example, the 5-diketone, acetylacetone, may show as much as one active hydrogen when treated with methylmagnesium iodide (186). In the other direction, resorcinol, which is conventionally written with two hydroxyl groups, reacts as if it contained one active hydrogen and one ketone group when the reaction is carried out in pyridine (79), although in anisóle as solvent the expected two active hydrogens are found (87). Results vary with the solvent and temperature (see below').…”

Section: Grignard Reagentsmentioning

confidence: 99%

Determination of Reactive Hydrogen in Organic Compounds

Olleman¹

1952

Anal. Chem.

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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...

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Section: Grignard Reagentsmentioning

confidence: 99%

Determination of Reactive Hydrogen in Organic Compounds

Olleman¹

1952

Anal. Chem.

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“…Little attempt has been made to discuss the reasons for anomalous results. Fuchs, Ishler, and Sandhoff (2) attribute the low values for certain acids to insolubility, and Lehman and Basch (8) suggest that a further contributory factor may be that the reaction takes place onK at the surface. Kohler, Stone, and Fuson (6) mention three possible difficultiesrelative insolubility of the substance, insolubility of intermediate products, and occurrence of successive reactions.…”

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Determination of Active Hydrogen Atoms

McAlpine¹,

Ongley²

1955

Anal. Chem.

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This work was done in an endeavor to obtain satisfactory analytical data on certain alkaloids. In Zerewitinoff determinations it was found that the influence of temperature is probably often restricted to promoting solution and liberating occluded gases, that the influence of solvent is relatively unimportant, and that the activity of the hydrogen atoms of active methylene groups varies considerably with environment.

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Zerewitinoff Determination

2010

Comprehensive Organic Name Reactions and Reagents

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The quantitative determination of active hydrogens in a chemical substance by means of adding methylmagnesium iodide in pentyl ether to the solution of substrate and quantitatively measuring the volume of gaseous methane evolved is generally known as the Zerewitinoff determination. In addition, Zerewitinoff extended this method to determine the active hydrogens of compounds with hydroxyl, amino, imino, and amido groups. It has been reported that methylmagnesium chloride is less reactive than corresponding bromide and iodide and is unstable when kept standing for a long time. The molecules that react with methylmagnesium iodide fall into two groups. Furthermore, the Zerewitinoff determination has also some limitations. It yields incorrect data for certain types of molecules and has problems with the picrotoxin series of compounds. Such inaccuracy of the Zerewitinoff determination may be partially caused by temperature and solvent effects. This method has been widely applied in early stages for the structural analysis for organic compounds.

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Determination of Active Hydrogen Using Grignard Reagent in Pyridine

Cited by 8 publications

References 8 publications

Determination of Reactive Hydrogen in Organic Compounds

Determination of Reactive Hydrogen in Organic Compounds

Determination of Active Hydrogen Atoms

Zerewitinoff Determination

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