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Chapter 14: Q.21558-14-49P (page 563)

Question: Rank the highlighted carbon atoms in each compound in order of increasing chemical shift.

a.

b.

Short Answer

Expert verified

Answer

a. Ca< Cb < Cc

b. Cc < Cb< Ca

Step by step solution

01

Chemical shift

13C spectroscopy gives a downfield (higher value) chemical shift and an upfield chemical shiftaccording to the non-equivalent chemical environment present around the atom which is under observation.

02

Explanation

a.

Labeled carbon

Ccis adjacent to the carbonyl oxygen which is an electronegative atom. Therefore, Cc has higher value of chemical shift. Cb is also close to carbonyl oxygen followed by Ca.

Therefore, the order of chemical shift value is shown as:

a. Ca < Cb < Cc

b.

Labeled carbon

Cahas higher value of chemical shift due to presence of sp2 hybridized atoms. Ccis adjacent to Br which is an electronegative atom. Therefore, CC has higher value of chemical shift. Cb is also close to the double bond.

Therefore, the order of chemical shift value is shown as:

b. Cc < Cb < Ca

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Most popular questions from this chapter

What splitting pattern is observed for each proton in the following compounds?

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Question: Treatment of 2-methylpropanenitrile [(CH3)2CHCN] with CH3CH2CH2MgBr, followed by aqueous acid, affords compound V, which has molecular formula C7H14O. V has a strong absorption in its IR spectrum at 1713 cm-1, and gives the following 1 H NMR data: 0.91 (triplet, 3 H), 1.09 (doublet, 6 H), 1.6 (multiplet, 2 H), 2.43 (triplet, 2 H), and 2.60 (septet, 1 H) ppm. What is the structure of V? We will learn about this reaction in Chapter 22.

How many lines are observed in the 13C NMR spectrum of each compound?

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Question: Compound C has a molecular ion in its mass spectrum at 146 and a prominent absorption in its IR spectrum at 1762cm-1 . C shows the following 1H NMR spectral data: 1.47 (doublet, 3 H), 2.07 (singlet, 6 H), and 6.84 (quartet, 1 H) ppm. What is the structure of C?

Question: How many 1H NMR signals does each natural product exhibit?

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