Methyl sampling

In the case of selective extraction of compounds from steam distillate after pH adjustment, about 1.5 L distillate were collected by co-distilling 200 g of powdered nuts with 2.5 L of water. The basic, neutral and acidic compounds were extracted using either methylene chloride or ether and the solvent was removed by distillation. In the case of the acidic fraction, the ether extract was methylated by refluxing with methanol-sulphuric acid (50 1) reagent for 2 hours. The methylated samples were washed free of acid and extracted with redistilled hexane, dried and stored frozen. 

Record42 later studied the same methylated samples in the ultracentrifuge. As expected from the polydisperse nature of all the samples, the molecular weight values (1.90(10) , 3.58(10) , 0.97(10) and 1.13(10) for the derivatives in Table III) were higher than the corresponding... 

Fig. 8.1.4. High-performance size-exclusion chromatograms of methylated samples of pine...

Both underivatised and methylated samples are examined because uracil herbicides give a mixture of products on methylation and should be chromatographed in their underivatised forms, whereas carboxylic acid pesticides, e.g. chlorinated phenoxy acid herbicides, are best examined as methyl derivatives. 

A portion of the photolytically degraded PBO was treated with diazoniethane to methylate any acid functions present. Half of this methylated sample was treated with MSTFA (Af-methy l-Af-lrimethy Isilyl-tri Auorcacetamide) to tri methyl sily I ate any alcohol groups. The two derivatized samples were examined under the standard GC-EIMS conditions used for the photolytically degraded PBO and the data obtained were compared with the data from (he photolytically degraded PBO. 

The methylated sample is dissolved in 50 mL of tetrahydrofuran and 5 g of sodium bicarbonate is added. The suspension is stirred and 5 mL of acetyl chloride is added. Stirring is continued overnight with the reaction mixture at room temperature. The solvent and excess acetyl chloride are removed by vacuum rotary evaporation at 30°C, and the product is partitioned between methylene chloride and water. Reaction by-products partition into water and the product partitions into methylene chloride. Emulsions may form during solvent extraction but they can be broken by addition of water saturated with sodium chloride. The methylene chloride is back-extracted twice with equivalent volumes of water, dried over sodium sulfate, and evaporated from the product. 

The content of free phenolic gronps in lignins has a major biochemical and technological signihcance. When thioacidolysis is performed on diazomethane-methylated samples, additional monomers 8-10 with methylated phenolic groups (Figure 2.6) are recovered [65,66], The total yield of thioacidolysis monomers is similar before... 

Percentage of Free Phenolic Groups in P-O-4 Linked H, G, and S Lignin Units, as Determined by Thioacidolysis of CHjNj Methylated Samples. The Reported Relative H/G/S Frequency is Based on Lignin-Derived Thioacidolysis Monomers (tr Trace Amount). The Lignin-Derived Monomers 1-3 and 8-10 are Outlined in Figure 2.6... 

The use of the blank serves to correct for the contributions that the retained fluorene makes to the spectra. This correction is most ideal when the total amount of fluorene is identical in the two samples and when methylated fluorene reagent makes only a minor contribution to the total spectral characteristics of the methylated sample. This situation is most closely approximated for the samples labeled blank and 1. This same condition does not hold for those samples labeled 2 and 3 because fluorene retention exceeds that of the blank sample. However, this perturbation will not affect the primary conclusions derived from the spectroscopic data. 

Carboxymethylcellulose was characterized by the analysis of completely carboxy-methylated samples. The depolymerized sample was then analyzed for 6-mono-O-,... 

Figure 2. Product Xul/Mn for end-methylated samples corresponding to Csi=0.17 (w/w) as a function of the square root of the molecular weight...

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