User:Vivek8032/sandbox

THE NITROGEN RULE INTRODUCTION: The molecular weights of compound only C, H, (o) are even, as those of molecules additionally containing an even number of compounds containing only C, H, N, (O) are even, as those of molecules additionally containing an even number of nitrogen atoms. The molecular weights of compounds containing only C,H,N,(O) are odd when the number of nitrogen is odd. PRINCIPLE: Nitrogen rule states that a molecule of even numbered molecular mass must contain absence of N or an even number of nitrogen atoms. An odd numbered molecular mass requires an odd number of nitrogen atoms. This rule holds for all compounds containing C, H, N, O, S and halogens as well as less usual atoms like P, B, Si, As etc. This principle may prove useful when attempting to solve organic mass spectrometry structures. FORMULATION OF THE RULE: Mass spectrometry generally operates by measuring the mass of ions. If the measured ion is generated by creating or breaking a single covalent bond then the nitrogen rule becomes reversed (odd numbered masses indicate even no. of nitrogen and vice versa). However, for each consecutive covalent bond that is broken or formed, the N rule again reverses. Inorganic molecules do not necessarily follow the rule. For example the nitrogen oxides NO and NO2 have an odd no. of nitrogen but even masses of 30 and 46. According to N rule, the two compounds C3H5NO2 and C2H7NS which contain one nitrogen atoms per molecule each have an odd molecular weight, while that of C, 6H7BrN2 is even. Example of nitrobenzene(C6H5NO2), the signal for molecular ion appears at m/e 123 i.e., odd numbered contains only one (odd number) nitrogen atom. The inclusion of any common stable isotope except O18 alters the use of nitrogen rule. The inclusion of any common stable isotope except O18 alters the use of nitrogen rule. -vivek pandey, amethi