The reaction mechanism of the Kolbe-Schmitt reaction of phenol and 2-naphthol has been investigated. An alkali metal phenoxide-CO2 complex is not an intermediate that can be easily transformed into a carboxylic acid, such as salicylic acid (SA) and p-hydroxybenzoic acid (pHBA). A direct carboxylation of phenoxide with CO2 takes place even at room temperature, and is competitive with the formation of the CO2 complex. The resulting complex decomposes thermally (above ca. 100 degrees C) to phenoxide, which then undergoes further competitive reactions. Experiments using a carbon-13 labeled complex support a mechanism of direct carboxylation, and not the mechanism via a CO2 complex. The reactivity, C-13 NMR and MOPAC/PM3 calculations suggest a new carbonate-like structure for the CO2 complex.

The study was conducted at the vegetable research farm of the Horticulture Research Centre, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur during the period 2006-2007 to investigate the effects of boron and zinc in presence of different levels of NPK fertilizers on quality of tomato. There were twelve treatment combinations which comprised four levels of boron and zinc viz., i) B0Zn0= 0 kg B + 0 kg Zn/ha, ii) B1.5Zn2.0= 1.5 kg B + 2.0 kg Zn/ha, iii) B2.0Zn4.0 = 2.0 kg B + 4.0 kg Zn/ha, iv) B2.5Zn6.0, 2.5 kg B + 6.0 kg Zn/ha and three levels of NPK fertilizers viz., i) 50% less than the recommended NPK fertilizer dose (50% <RD), ii) Recommended NPK fertilizer dose (RD), iii) 50% more than the recommended NPK fertilizer dose (50% >RD). The highest pulp weight (88.14%), dry matter content (5.34%), TSS (4.50%), acidity (0.47%), ascorbic acid (10.95 mg/100g), lycopene content (112.00 μg/100g), chlorophyll-a (41.00μg/100g), chlorophyll-b (56.00 μg/100g), marketable fruits at 30 days after storage (67.48%) and shelf life (16 days) were recorded with the combination of 2.5 kg B+ 6 kg Zn/ha and recommended dose of NPK fertilizers (N= 253, P= 90, and K= 125 kg/ha). Keywords: Quality of tomato; boron and zinc; NPK fertilizer. DOI: 10.3329/bjar.v35i3.6454Bangladesh J. Agril. Res. 35(3) : 475-488

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The experiment to determine the effects of KNO 3 and urea in manipulating the harvesting time and increasing yield as well as quality of nine years old mango (Mangifera indica L.) cv. Amrapali plants was carried out at the BAU Germplasm Centre, Department of Horticulture, Bangladesh Agricultural University, Mymensingh during the period from September 2006 to July 2007. The five treatments included in the experiment were potassium nitrate at 4%, 6% and 8%; urea at 2% and 4% and the control (water spray). Foliar spraying of urea at 4% exhibited better performance in relation to terminal shoot length, number of leaves and leaf area and potassium nitrate at 4% gave superior results with respect to length and breadth of panicle and number of secondary branches per panicle compared to control. The plants sprayed with KNO 3 at 4% expressed earlier panicle appearance by 17 days as compared to delayed appearance of panicle in untreated control plants. The plants received KNO 3 at 4% produced the highest number of panicles per plant (220.67) whereas the control plants had the least number of panicles (107.67). Regardless of concentration, KNO 3 and urea manifested slightly earlier harvest (5 days) compared to control. Plants treated with KNO 3 at 4% noted the highest number of fruits per plant (136.67) compared to control (62.67). The treatment urea at 4% resulted in the biggest fruit (202.83g) and the control plants exhibited the smallest fruit (175.00g). Potassium nitrate at 4% gave maximum yield (23.14 kg/plant) as compared to minimum yield (9.12 kg/plant) in the control (water spray).

It was found that the carboxylations of magnesium, calcium, and barium phenoxides with carbon dioxide at 260 °C produced salicylic acid and dicarboxylic acids (4-hydroxyisophthalic acid and 2-hydroxyisophthalic acid) in very high yields (80–100%), exceeding that of the ordinary Kolbe–Schmitt reaction. The orientation (ortho/para ratio) was controlled not only by chelations of the intermediate with alkaline earth metal (Mg, Ca, Ba) ions, resulting in salicylic acid, but also by the sizes of metal ions (Rb, Cs), giving p-hydroxybenzoic acid in a much higher ratio than the widely used method with potassium or sodium phenoxide. These alkaline earth metals worked to produce 3-hydroxy-2-naphthoic acid by the reaction of 2-naphthoxide with carbon dioxide, but the yield of 6-hydroxy-2-naphthoic acid was comparable to that of 3-hydroxy-2-naphthoic acid when cesium or rubidium 2-naphthoxide was employed. Considerably high yields (∼60%) of 6-hydroxy-2-naphthoic acid, a monomer of one of the best liquid-crystal polymers, was attained by the carboxylation of cesium or rubidium 2-naphthoxide in the presence of potassium or sodium carbonate, where the alkali metal ion was supposed to increase the reactivity of the substrate. The formation of “binol” was observed in the preparation of 2-naphthoxides with metal hydroxides, especially with copper(II) ion.