Spin-Spin Splitting Unlike in the H NMR spectrum of 1, 2, 2-trichloropropane on the previous page, most peaks are not single lines(singlets). In fact, the multiplicity of a peak(singlet, doublet, triplet) provides even more information about the structure of a molecule. This is because protons on adjacent atoms communicate with eachother In simple systems, n adjacent protons cause splitting into n+ l peaks For example, look at the spectrum of 1-chloropropane There are three inequivalent types of protons in this molecule(Hy h2, H3) It is easy to assign chemical shifts to the appropriate protons because you already know that chlorine is an electron withdrawing group The protons closest to the chlorine will have the least electron density (deshielded, downfield), and the protons furthest from the chlorine will have the most electron density(shielded, upfield). Using this reasoning, you can assign A=Hlb=H2, C=H Now, let's look at the multiplicity of the three peaksSpin-Spin Splitting • Unlike in the 1 H NMR spectrum of 1,2,2-trichloropropane on the previous page, most peaks are not single lines (singlets). • In fact, the multiplicity of a peak (singlet, doublet, triplet) provides even more information about the structure of a molecule. This is because protons on adjacent atoms communicate with eachother. In simple systems, n adjacent protons cause splitting into n + 1 peaks. • For example, look at the spectrum of 1-chloropropane: H1 H1 H3 H3 C C Cl C H3 H2 H2 • There are three inequivalent types of protons in this molecule (H1, H2, H3) . • It is easy to assign chemical shifts to the appropriate protons because you already know that chlorine is an electron withdrawing group. • The protons closest to the chlorine will have the least electron density (deshielded, downfield), and the protons furthest from the chlorine will have the most electron density (shielded, upfield). Using this reasoning, you can assign: A = H1, B = H2, C = H3 • Now, let's look at the multiplicity of the three peaks. . . 8