D) cannot be determined from information given 16) Which of the following reason
ID: 566728 • Letter: D
Question
D) cannot be determined from information given 16) Which of the following reasons best explains why aromatice protons have a larger chemical shit h protons one carbon removed from a halogen? A) An aromatic ring is more electron withdrawing than a halogern B) A halogen is more electron withdrawing than an aromatic ring. C) Electron movement induces a magnetic field opposing the external field D) Electron movement induces a magnetic field reinforcing the external cas codignals in its IH NMIR spectrum, a tripltand a quinter? A) BrCH2CH2CH2Br B) BrCH2CH2CH2CI C) (CH3)2CHCH CH3)2 D) CH3CH2CH CH13 below? of molecular formula CallyCl fits boh the 'H NMR and C NMR spectra shown 11 107Explanation / Answer
1)The electrons in the aromatic ring such as bezene are highly delocalised. This circulation of electrons produces ring currents. This ring current produces the induced magnetic field around the aromatic compound. The induced magnetic field is opposed to applied magnetic field inside aromatic ring but aligned to applied magnetic field outside the aromatic ring. So protons present outside the aromatic ring has increased magnetic field also called as paramagnetic shift causes deshielding of proton. so the aromatic proton appears at higher chemical shift values.
2)correct option is A (BrCH2CH2CH2Br) . Number of signals in NMR is equal to number of chemicaly nonequivalent protons. In the above compound there as two chemically nonequivalent protons. One is four protons on C1 and C3, other is two protons on C2. So the four protons give triplet and the two protons give quintet.
3) correct option is B.The chlorine attached carbons show chemical shift values at nearly 4. C1 shows a triplet and C3 shows multiplet. The C2 and C4 shows values at nearly 1. C2 shows multiplet and C4 shows doublet.
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