A compilation of the S—O symmetric and asymmetric stretching frequencies is given for a large number of compounds containing an —SO2— group. It is shown that a linear relationship between is valid for a large number of sulphuryl and polysulphuryl compounds and that the actual frequencies depend in a systematic manner on the electronegativities of the attached groups. These relationships have proved very useful in assigning and in some cases reassigning the S—O bands in the infrared and Raman spectra of a number of sulphuryl compounds. It is pointed out that there is a relationship between the SO2 frequencies of some sulphonic acids and their acid strengths.The calculation of values for group electronegativities from the vibration frequencies of the P=O and SO2 groups is discussed.

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Characteristic vibrations of the sulphuryl group

Wood has an excellent mechanical performance, but wider utilization of this renewable resource as an engineering material is limited by unfavorable properties such as low dimensional stability upon moisture changes and a low durability. However, some wood species are known to produce a wood of higher quality by inserting mainly phenolic substances in the already formed cell walls a process so-called heartwood formation. In the present study, we used the heartwood formation in black locust (Robinia pseudoacacia) as a source of bioinspiration and transferred principles of the modification in order to improve spruce wood properties (Picea abies) by a chemical treatment with commercially available flavonoids. We were able to effectively insert hydrophobic flavonoids in the cell wall after a tosylation treatment for activation. The chemical treatment reduced the water uptake of the wood cell walls and increased the dimensional stability of the bulk spruce wood. Further analysis of the chemical interaction of the flavonoid with the structural cell wall components revealed the basic principle of this bioinspired modification. Contrary to established modification treatments, which mainly address the hydroxyl groups of the carbohydrates with hydrophilic substances, the hydrophobic flavonoids are effective by a physical bulking in the cell wall most probably stabilized by pi-pi interactions. A biomimetic transfer of the underlying principle may lead to alternative cell wall modification procedures and improve the performance of wood as an engineering material.

Flavonoid insertion into cell walls improves wood properties

As an engineering material derived from renewable resources, wood possesses excellent mechanical properties in view of its light weight but also has some disadvantages such as low dimensional stability upon moisture changes and low durability against biological attack. Polymerization of hydrophobic monomers in the cell wall is one of the potential approaches to improve the dimensional stability of wood. A major challenge is to insert hydrophobic monomers into the hydrophilic environment of the cell walls, without increasing the bulk density of the material due to lumen filling. Here, we report on an innovative and simple method to insert styrene monomers into tosylated cell walls (i.e. –OH groups from natural wood polymers are reacted with tosyl chloride) and carry out free radical polymerization under relatively mild conditions, generating low wood weight gains. In-depth SEM and confocal Raman microscopy analysis are applied to reveal the distribution of the polystyrene in the cell walls and the lumen. The embedding of polystyrene in wood results in reduced water uptake by the wood cell walls, a significant increase in dimensional stability, as well as slightly improved mechanical properties measured by nanoindentation.

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Improvement of wood material properties via in situ polymerization of styrene into tosylated cell walls

Infrarotspektroskopische untersuchungen an aromatischen sulfochloriden

The Raman and infra-red spectra of H3CSO3H and some of its salts have been obtained, with Raman polarization data for the acid.



An interpretation of the spectra is given and force constants have been calculated.

The Raman and infra‐red spectra of methane‐sulphonic acid and the methanesulphonate ion

The Raman spectra of benzene-, p-chlorobenzene-, p-bromobenzene-, p-methoxybenzene-, and o-, m-, and p-toluene sulphonyl chlorides and fluorides and methylbenzene sulphonate are recorded as well as the infra-red absorption bands of liquid benzene sulphonyl chloride and fluoride between 650 and 3100 cm.-l. A frequency c. 375 cm.-1 is characteristic of the S-Cl bond in sulphonyl chlorides and a strong band at c. 1210 cm.-1 is characteristic of the sulphonyl fluoride group. A Raman band at c. 1080 cm.-l in the chlorides and c. 1095 cm.-l in the fluorides appears to be associated with aromatic sulphonyl derivatives. There is such a band at 1094 cm.-1 in the Raman spectrum of methyl benzene sulphonate.

AN Hambly

Papers

The raman spectra of some aromatic sulphonyl Halides