Is the n 1 Rule Ever Really Obeyed

In a linear chain, the n + 1 Rule is strictly obeyed only if the vicinal interproton coupling constants ( J) are the same for every successive pair of carbons. 

Condition under which the n + 1 Rule is strictly obeyed 

In many molecules Jab is only slightly different from J c- This leads to peak broadening in the multiplet, since the lines do not quite overlap. (Broadening occurs because the peak separation in 

FIGURE 5.27 Construction of a quintet for a methylene group with four neighbors all coupled to the same extent. 

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