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我们常常碰到某些条件不充分的确定有机物分子式的计算题,这类题,用常规方法难以求解。本文举例说明几种特殊的求解策略,供大家参考。一、通式法例1 已知某烃的蒸气对氢气(相同状况下)的相对密度为89,求该烃分子式。解析:该烃的分子量M=89×2=178设烃的分子式为C_xH_y,则有:12x+y=178,y=178-12x因为2x+2≥y≥2(烃分子中氢原子数的最小值为2,如C_2H_2,最大值不超过烷烃中的2x-2)所以2x+2≥178-12x≥212.6≤x≤14.7又因为x,y均为正整数
We often encounter certain conditions that are insufficient to determine the molecular formula of organic matter. Such questions are difficult to solve with conventional methods. This article illustrates several special solution strategies for your reference. First, the general formula 1 is known that the relative density of a certain hydrocarbon vapor to hydrogen (under the same conditions) is 89, find the hydrocarbon formula. Analysis: The molecular weight of the hydrocarbon M = 89 × 2 = 178 set hydrocarbons formula C_xH_y, then there are: 12x + y = 178, y = 178-12x because 2x + 2 ≥ y ≥ 2 (hydrocarbon molecules in the number of hydrogen atoms The minimum value is 2, such as C_2H_2, the maximum value does not exceed 2x-2 in the alkane) so 2x+2≥178-12x≥212.6≤x≤14.7 because x and y are positive integers