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Microwave irradiation provides a way for flash heating as an alternative to standard thermal heating in chemical reactions. This technology has been employed to drastically reduce reaction times and even modify selectivity. In addition to this feature, the use of microwave irradiation may outperform conventional reaction conditions in other aspects, such as easier workup, reduction of the usual thermal degradation products, reduction of toxic and expensive quantities of solvents (green chemistry), and reduction of secondary products. Also, microwave irradiation has proven to be of benefit particularly for reactions under dry media (i.e., in the absence of solvents or solid support) and reactions without catalysts. Our goal is to extend this technology to the academic laboratory and introduce organic chemistry students to microwave-assisted reactions. Thus, we designed an inquiry-based laboratory experience based on the use of a microwave oven as a means for a comparative study of the effect of different catalysts in the synthesis of aspirin. The results, scope and limitations of this study are discussed in the article.

The Atlantic sharpnose shark Rhizoprionodon terraenovae (Richardson) is a small carcharhinid that is a common year-round resident along the southeast coast of the United States. It is viviparous and its embryos develop an epithelio-vitelline placenta. Females enter shallow water to give birth in late May and early June. Mating occurs shortly after parturition, and four to seven eggs are ovulated. Fertilized eggs attain the blastoderm stage in early June to early July. Separate compartments for each egg are formed in the uterus when the embryos reach 3-30 mm. Embryos depend on yolk for the first 8 weeks of development. When embryos reach 72 mm their yolk supply is nearly depleted and they shift to matrotrophic nutrition. When the embryos reach 40-55 mm, placental development begins with the vascularization of the yolk sac where it contacts the uterine wall. Implantation occurs at an age of 8-10 weeks by which time the embryos reach 70-85 mm. The expanding yolk sac engulfs the maternal placental villi, and its surface interdigitates with the villi to form the placenta. The rest of the lumenal surface of the uterus is covered by non-placental villi that appear shortly after implantation. Histotrophe production by the non-placental villi begins just after their formation. The placenta grows continuously during gestation. The egg envelope is present throughout gestation, separating maternal and fetal tissues. Embryos develop numerous appendiculae on the umbilical cord. Young sharks are born at 290-320 mm after a gestation period of 11 to 12 months. © 1993 Wiley-Liss, Inc.

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