發送短信 : Rotational isomerism in 2,3-dinitro-2,3-dimethylbutane

 _____       ___     _    _     ______   ______   
|  __ \\    / _ \\  | || | ||  /_   _// |      \\ 
| |  \ ||  / //\ \\ | || | ||   -| ||-  |  --  // 
| |__/ || |  ___  ||| \\_/ ||   _| ||_  |  --  \\ 
|_____//  |_||  |_|| \____//   /_____// |______// 
 -----`   `-`   `-`   `---`    `-----`  `------`