摘要:

Three alkali lignins from different industrial origins were reacted with formaldehyde under acidic conditions. Depending on the conditions, the lignins were crosslinked and hydroxy-methylated at positions 2 and 6 on the lignin phenylproponoid units.

ISSN:0277-3813    

DOI:10.1080/02773818908050282

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Lignin model compounds hydroxymethylated at the 2 and 6 positions reacted with phenol or resorcinol to afford methylene linked products. Optimum conditions for the reactions were established.

ISSN:0277-3813    

DOI:10.1080/02773818908050283

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A free phenolic condensed tannin model compound, 4-(2,4,6-trihydroxyphenyl)flavan-3,3′,4′,5,7-pentaol, was synthesized in high yield from phloroacetophenone dibenzyl ether and protoca-techualdehyde dibenzyl ether. Condensation of the 2,3-trans-3,4-cis-flavan-3,4-diol with phloroglucinol in the presence of a Lewis acid, TiCl4, proceeded with high stereoselectivity, to give only the 2,3-trans-3,4-trans isomer in over 90percnt; yield. The reactivity of this model compound might be compared with those of other model compounds to determine the effect of the hydroxyl groups in the A, B, and D rings on the reactivity of the C ring. Furthermore, this synthetic route might be applied to the synthesis of artificial tannin derivatives.

ISSN:0277-3813    

DOI:10.1080/02773818908050284

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The needles and twigs of black spruce—Picea mariana(Mill.) B.S.P.—were analyzed for the composition of their essential oil after having been submitted to hydrodistillation. The composition of the essential oil is significantly influenced by the preparation of the samples: whether prepared as two-cm pieces or macerated in a blender. Depending upon the preparation of the samples, the major components are, respectively: α-pinene (7.4 and 13.5%), camphene (14 and 21.2%) and bornyl acetate (41.8 and 29.6%). Sixteen constituents are reported for the first time.

ISSN:0277-3813    

DOI:10.1080/02773818908050285

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Kraft pulping of Douglas-fir(Pseudotsuga menziesii)was carried out from 90°C to a final temperature of 170°C at a heating rate of 1°C/min. At various stages of delignification, middle lamella and secondary wall enriched fractions were isolated from pulps and analyzed by nucleus exchange and alkaline nitrobenzene oxidation reactions to reveal the dissolution and condensation of lignin building units in these two morphological regions. For non-delignified Douglas-fir, the ratio of condensed/non-condensed phenyl nuclei varied significantly between middle lamella and secondary wall lignins. Values of 2.5/1 and 1/1 were found for middle lamella and secondary wall lignins, respectively. At early stages of pulping (below 110°C), the removal of phenyl nuclei in secondary wall lignin was due entirely to the dissolution of non-condensed phenyl nuclei. After the temperature reached 160°C, a rapid formation of diphenylmethane moieties in middle lamella was observed, whereas the formation of such moieties in secondary wall occurred after the peak pulping temperature (170°C) was reached.

ISSN:0277-3813    

DOI:10.1080/02773818908050286

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

E. regnanscold soda pulp has been bleached to a high brightness (about 87) in a single-stage treatment with alkaline hydrogen peroxide, and also in 2- and 3-stage sequences which used sodium borohydride in the second stage. The sequences did not provide further appreciable increases in the brightness level, but the borohydride-treated pulp showed greater brightness stability when irradiated with UV light, even when the pulp had been subjected to a third stage hydrogen peroxide bleach.

ISSN:0277-3813    

DOI:10.1080/02773818908050287

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Although chromated copper arsenate (CCA) is one of the most important treatment methods for the prevention of decay in wood, the nature of wood/CCA reactions are not clear. The current study was undertaken to elucidate the nature of chemical reactions occurring between the components of the treating solution and the constituents of wood. Small, clear Southern pine samples were treated with six different preservative solutions (Cr; Cr/Cu; Cr/As; CCA-A; CCA-B; CCA-C), at 6.4 and 40 Kg/m3(0.4 and 2.5 pcf) retentions, and compared to water treated and untreated controls. Samples were dried following treatment and analyzed by diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). Evaluation of DRIFT data indicated that the preservative components reacted with the aromatic and carbonyl groups in wood.

ISSN:0277-3813    

DOI:10.1080/02773818908050288

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A systematic investigation of cement-hardening inhibitory components from the heartwood of western red cedar (Thuja plicataD. Don) led to the isolation of three lignans. Their inhibitory indices confirmed that plicatic acid has a strong inhibitory effect, and two phenolic lactones, plicatin and dihydroxythuja-plicatin, a weak effect.

ISSN:0277-3813    

DOI:10.1080/02773818908050289

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0277-3813    

DOI:10.1080/02773818908050281

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor