Retsch GmbH

A mixture of aldehyde 1 (0.5 mmol), malononitrile (0.5 mmol) and Hantzch 1,4-dihydropyridine 2 (0.51 mmol) was introduced, together with a stainless ball of 7.0 mm diameter, into a stainless steel jar (5 mL). The same mixture vessels were also introduced into a second, parallel jar. The two reaction vessels were closed and fixed on the vibration arms of a ball-milling apparatus (Retsch MM200 mixer mill, Retsch GmbH, Haan, Germany) and vibrated vigorously at a rate of 1800 rpm (30 Hz) at room temperature for 90 min. 

Retsch GmbH Co. KG Rheinische StraBe 36 42781 Haan Germany... 

Each ground mixture of LOR and P-CD (LOR/P-CD) or LOR and HP-P-CD (LOR/HP-P-CD) with a 1 1 molar ratio was respectively prepared in an oscillatory ball mill (Mixer Mill MM301, Retsch GmbH Co., Germany) with 15 Hz oscillation frequency. About 0.2 g of powder sample was placed in a 25 ml volume stainless steel milling jar containing two 15 mm diameter stainless steel balls, and then oscillated. In the grinding process, the sample was withdrawn at the prescribed intervals for further examination (Lin et al, 2010). 

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