Determination of Methoxyl and Ethoxyl Groups in Acetals and Easily Volatile Alcohols

Hoffman, D. O.; Wolfrom, M. L.

doi:10.1021/ac60004a004

Cited by 21 publications

(6 citation statements)

References 20 publications

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“…302 ' 303 For rapid identification of methyl ether, methylamino, and methylthio groups, and for quantitative determination of such derivatives, n.m.r. 302 ' 303 For rapid identification of methyl ether, methylamino, and methylthio groups, and for quantitative determination of such derivatives, n.m.r.…”

Section: Determination Of Ethersmentioning

confidence: 99%

Analytical Methods for Carbohydrates

Aminoff¹,

Binkley²,

Schaffer³

et al. 1970

The Carbohydrates

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Section: Determination Of Ethersmentioning

confidence: 99%

Analytical Methods for Carbohydrates

Aminoff¹,

Binkley²,

Schaffer³

et al. 1970

The Carbohydrates

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“…and finally dried to constant weight in a vacuum desiccator. This product was then analyzed for methoxyl (9), and the values reported (Table 11) represent the mean of two determinations which differed from each other by less than one per cent of the Iclason lignin. The alkaline nitrobenzene oxidations were made on small samples (ca.…”

Section: General Reaction Procedzlrementioning

confidence: 99%

The Isolation and Oxidation of Aspen Lignins

Pepper¹,

Hagerman²

1954

Can. J. Chem.

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A study has been made of the conditions affecting the isolation of a lignin fraction by a procedure involving a moderate temperature catalytic hydrogenation of pre-extracted aspen wood meal. The effect of varying the initial hydrogen pressure, the catalyst, the time and maximum temperature of reaction, and the nature and acidity of the suspending medium were studied. The weight of the residual pulp, the effectiveness of lignin removal, the weight and methoxyl content of the resulting chloroform-soluble fraction containing the lignin, and the yields of vanillin and syringaldehyde obtained by the alkaline nitrobenzene oxidation of this same fraction were the factors serving as the bases for comparison.Initial hydrogen pressures greater than 500 p.s.i.g. were not required, although below this value there was some loss of efficiency. Neither the use of water or dioxane alone was satisfactory as a suspending medium, but the mixed aqueous-organic medium was required to remove the released lignin. Considering the resultant slight acidity of the reaction product, it is suggested that in such an isolation two separate stages are involved: that of the water functioning to wet and permeate the wood and serve as the acidic medium and that of the organic solvent phase functioning to remove the liberated lignin after the hydrolytic cleavage.Data are presented and interpreted to indicate the existence of a lignin-carbohydrate complex which is cleaved under the conditions of catalytic hydrogenation. Under the conditions of these experiments practical temperatures for lignin removal are in the range 170 – 180 °C. for an aqueous-organic solvent medium, but some thirty degrees lower for an 85% acetic acid medium. Although it has been possible to isolate all the lignin, with good methoxyl recovery, consistently no more than approximately fifty per cent of the required aldehydes is obtainable on oxidation. The increasing value of the syringaldehyde – vanillin ratio with increasing temperature is due to a decreased vanillin yield.Indications are that the use of copper chromium oxide may be preferred over Raney nickel as a catalyst for this isolation procedure.

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“…Methoxyl analyses were carried out by the method of Hoffman and Wolfrom (13). A Glas-Col heating mantle for the reaction flask was found to give less bumping and better all-round performance than did an ordinary flame.…”

Section: Accessibility To Thallous Etlzylatementioning

confidence: 99%

The Reactivity of Cellulose: II.WATER Sorption, Heats of Wetting, and the Reactions With Thallous Ethylate in Ether, Nitration Mixtures, and Heavy Water of Cotton Linters Alternately Wetted With Water and Dried

Brickman¹,

Dunford²,

Tory³

et al. 1953

Can. J. Chem.

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Cotton linters dewaxed with benzene and alcohol possess a slightly expanded structure attributed to the swelling effect of the alcohol. Storage causes a partial collapse of the linters especially so when moisture is present. Wetting with water followed by rigorous drying produces a marked reduction in accessibility, but with each additional wetting-drying cycle accessibility of the dried linters increases slightly as measured by reaction with thallous ethylate in ether, a nitration mixture, and in hydrogen-deuterium exchange. Differences in nitration found for limited reaction times are obliterated when these reaction times are extended. Increasing accessibility due to repeated wetting and drying is accon~panied by lower water sorption and smaller heats of wetting. This anomaly is due to the fact that cellulose sanlples obtained by alternately wetting and drying dewaxed linters, when stored with a desiccant, compete for the limited amount of water present and adsorb moisture in proportion to their accessibility. Upon further exposure to water the sample of least accessibility, having adsorbed less water, can now adsorb to a greater extent than do the linters of somewhat greater accessibility.The evidence indicates that the difference in accessibility occasioned by repeated wetting and drying is of a physical rather than chemical nature. INTRODUCTIONThe accessibility of cellulose to reagents is a matter of colisiderable practical and theoretical importance and in recent years has been given a great deal of attention (6,12,16,19,21,28). I t has been shown quite conclusively that this accessibility is influenced by the previous history of the cellulose sufficiently that uniform reactivity is obtained only by the observation of great care in the choice and processing of the raw material (14, 25).The association of cellulose with water throughout most of its history has provoked enquiries regarding the influence that water has upon the properties of cellulose. I t is generally believed that water itself exercises only a swelling effect, producing nothing more than an increase in the amount of accessible cellulose a t the expense of that portion less highly organized. However, recent work indicates that a slight change in dimensions of the unit cell occurs when dry mercerized ramie, spun viscose, or regenerated acetate fibers are wetted (15). Furthermore, lengthy exposure of wet cellulose t o oxygen (air) or ozone is reported to produce some degradation of the macromolecule (3,4). The removal of water from cellulose by direct drying methods is accompanied by a decrease 1 n/Ia?~uscript

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Determination of Methoxyl and Ethoxyl Groups in Acetals and Easily Volatile Alcohols

Cited by 21 publications

References 20 publications

Analytical Methods for Carbohydrates

Analytical Methods for Carbohydrates

The Isolation and Oxidation of Aspen Lignins

The Reactivity of Cellulose: II.WATER Sorption, Heats of Wetting, and the Reactions With Thallous Ethylate in Ether, Nitration Mixtures, and Heavy Water of Cotton Linters Alternately Wetted With Water and Dried

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