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d) 2-(BenzyIsulfinyl)ethyl Cyclohexyl Disulfide (15).Cyclohexanethiol (1.16 g, 10.0 mmol) and Na in 10 mL of MeOH reacted with 10 mmol of 17 in MeOH (25 mL) in only 6 min at -15 °C. After the procedure of (a) as usual, chromatography (5.5 X 8 cm column) gave a fraction of R¡ 0.53 that yielded 2.20 g (70%)

The ethanol extraction from microwave‐pretreated and untreated canola seeds is studied. Two process are used to obtain the oil: in a control process (P1), the solvent‐free total extract (E) is washed with hexane, obtaining an oil fraction (OF). The second process (P2) consists of the partial evaporation of the solvent of the total extract (E), cooling, centrifugation, and separation by decantation of the generated phases: oil‐rich phase (OF + Ethanol), solvent‐rich phase (EthF + Ethanol), and solid phase (SF); and then evaporating the solvent to obtain OF and an extract of soluble in the phase rich in ethanol (EthF). No significant differences due to microwaves are detected in the yields. P2 gave mean yields of 32.8%db of OF, lower than obtained with P1 (42.1%db), 4.2%db of precipitated solids, and 7.7%db of EthF, which present a mean content of hexane‐solubles of 5.1%db. However, the quality analysis shows a smaller oxidative damage and an increase in canolol content due to the microwaves. P2 also generates an antioxidant‐rich byproduct, allowing to recover the canolol prior to a refining stage of the oil. Practical Applications: The use of organic solvents for the extraction of vegetable oils have some disadvantages, such as health and safety problems. At the same time, ethanol has begun to be studied as an alternative solvent due to its lower production costs than other alternative solvents, and to the fact that it is recognized as a “bio‐renewable” solvent. Numerous studies have shown the extraction of oil and impurities obtained with ethanol. However, no method have been developed for obtaining an insoluble‐free canola oil from the extract obtained with ethanol without using hexane. In addition, a favorable effect of the canolol content pretreated with microwaves in the canola oil is reported, nevertheless, the canolol is eliminated during the refining stage of the crude oil. The hexane‐free development process allows to obtain canola oil and an antioxidant‐rich byproduct, allowing to recover the canolol prior to a refining stage of the oil. Green solvent (ethanol) extraction from microwave‐pretreated canola seeds and a hexane‐free separation process is developed. The results show a high yield of canola oil and the production of an antioxidant‐rich byproduct.

The influence of microwave pretreatment on the oil yield (solvent extraction) and oil quality of canola was studied. Response surface methodology was used to analyze the variables of microwave pretreatment, working with two microwave powers 80 and 100% (457 and 607 W, respectively, referred absorbed power of 1 L of water). The independent variables were initial moisture content (5-10% dry basis) and pretreatment time (10-350 s), considering five levels. Second-order polynomial equations were used for oil yield, and first-order polynomial for final moisture content. The response models obtained were validated with independent experiments. Under optimal pretreatment conditions, no significant differences were detected in acidity, fatty acid profile and tocopherol content between the unpretreated and pretreated samples. However, significant differences were observed for peroxide index. PRACTICAL APPLICATIONSCanola oil is classified as one of the healthiest vegetable oils due to its fatty acid composition (low in saturated fatty acids and high in essential fatty acids). Vegetable oils are conventionally obtained by pressing or solvent extraction, the latter being the more efficient method. However, the use of organic solvents has some disadvantages such as health and safety issues, emission of volatile organic compounds, high operating costs and poor oil quality caused by the high temperatures of the process. Microwave pretreatment applied to canola seeds is a new technique that offers shorter processing times and lower energy consumption and provides better yields within short times and with reduced solvent use in the extraction step, maintaining the quality of the oil.

The phenomenon and kinetics of the ethanol extraction of canola oil from microwave-pretreated seeds was studied using a Fick’s diffusion model. The extraction was performed in a batch system at constant temperature (313–333 K) at different times (300–64 800 s); then the total solvent-free extracts (SFE) were washed with hexane, obtaining oil as a hexane-soluble fraction (HSE) along a hexane-insoluble fraction. The values of the fitted parameters were different from those obtained by hexane extraction, showing an influence of the solvent on the kinetic parameters. A comparison of SEM images of pre-extracted, post-extracted with ethanol and post-extracted with hexane meals showed a dilution of the structural matrix with ethanol, not observed in post-extraction samples with hexane. This would indicate that a microwave-pretreatment is not necessary for the ethanol extraction of canola oil under the studied conditions, although it is important for breaking seed structures to facilitate the conventional extraction with hexane.

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