13.8 Splitting Patterns: The Ethyl Group Coupling of nuclear spins requires that the nuclei split each other's signal equally The separation between the two halves of the methyl doublet in 1, 1-dichloroethane is qual to the separation between any two adjacent peaks of the methine quartet. The extent to which two nuclei are coupled is known as the coupling constant J and in simple cases is equal to the separation between adjacent lines of the signal of a particular pre ton. The three-bond coupling constant Jab in 1, l-dichloroethane has a value of 7 Hz The size of the coupling constant is independent of the field strength, the separation between adjacent peaks in 1, 1-dichloroethane is 7 Hz, irrespective of whether the spec trum is recorded at 200 MHz or 500 Mhz 13. 8 SPLITTING PATTERNS: THE ETHYL GROUP At first glance, splitting may seem to complicate the interpretation of NMR spectra. In fact, it makes structure determination easier because it provides additional information It tells us how many protons are vicinal to a proton responsible for a particular signal. With practice, we learn to pick out characteristic patterns of peaks, associating them with particular structural types. One of the most common of these patterns is that of the ethyl group, represented in the NMR spectrum of ethyl bromide in Figure 13 13 H3 801.701.60 CH, BrCh,ci CHCI3 TMS 3.0 0.0 Chemical shift(8, Ppm) FIGURE 13 13 The 200-MHz H NMR spectrum of ethyl bromide showing the characteristic triplet-quartet pattern of an ethyl group Back Forward Main MenuToc Study Guide ToC Student o MHHE WebsiteCoupling of nuclear spins requires that the nuclei split each other’s signal equally. The separation between the two halves of the methyl doublet in 1,1-dichloroethane is equal to the separation between any two adjacent peaks of the methine quartet. The extent to which two nuclei are coupled is known as the coupling constant J and in simple cases is equal to the separation between adjacent lines of the signal of a particular pro￾ton. The three-bond coupling constant 3 Jab in 1,1-dichloroethane has a value of 7 Hz. The size of the coupling constant is independent of the field strength; the separation between adjacent peaks in 1,1-dichloroethane is 7 Hz, irrespective of whether the spec￾trum is recorded at 200 MHz or 500 MHz. 13.8 SPLITTING PATTERNS: THE ETHYL GROUP At first glance, splitting may seem to complicate the interpretation of NMR spectra. In fact, it makes structure determination easier because it provides additional information. It tells us how many protons are vicinal to a proton responsible for a particular signal. With practice, we learn to pick out characteristic patterns of peaks, associating them with particular structural types. One of the most common of these patterns is that of the ethyl group, represented in the NMR spectrum of ethyl bromide in Figure 13.13. 13.8 Splitting Patterns: The Ethyl Group 503 4.0 3.0 2.0 1.0 0.0 Chemical shift (δ, ppm) 9.0 8.0 7.0 6.0 3.6 3.5 3.4 3.3 1.80 1.70 1.60 5.0 CHCl3 TMS BrCH2CH3 CH3 CH2 FIGURE 13.13 The 200-MHz 1 H NMR spectrum of ethyl bromide, showing the characteristic triplet–quartet pattern of an ethyl group. Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website