solve DIRECTIONS: Please answer moment? o iB All 1. Which of the following nucle

Question

solve DIRECTIONS: Please answer moment? o iB All 1. Which of the following nuclei will have a magnetic 12 -2. An unknown compound A has the molecular formula CMO-Bas the structure of compound A? the molecular formula C,H,O, Based on the following 'H NMR spectrum, what is sl A) O B) D) 3. The C NMR spectrum of an unknown compound shows 4 absorptions and the 'H NMR spectrum sh absorptions. Which of the following compounds is the unknown compound? ows 4 CH3 CH3 A) CH B) c) Ct D) CH CH3 CH3 4, which of the following compounds will have the longest wavelength absorption? A) C) O D) -5. Which of the following statements regarding 1,2-or 1,4-conjugate addition of HBr to 1,3-butadiene is FALSE? A) The kinetic product, 3-bromo-1-butene, arises from the more stable carbocation intermediate. 8) The thermodynamic product, 1-bromo-2-butene, is the more stable product. ) The kinetic product is favored by carrying out the reaction at high temperature. ) Formation of the two products arises from a common resonance stabilized carbocation intermediate.

Explanation / Answer

1. Of the given nuclei

E) All

All of them have magnetic moment. The magnetic moment is important in the NMR measurement technique.

2. The compound with the molecular formula C4H8O2 has a structure,

A)

peak at around 2 ppm (singlet) for 3H is for CH3 next to C=O

peak at around 3.2 ppm (singlet) for 3H is for CH3 next to O

peak at 4.5 ppm (singlet) for 2H is for CH2 next to an O and a C=O so most downfield.

3. The compound with 4 absorptions in 13C NMR would be,

A)

It has four types of C's in it.

4. Of the given compound,

B)

will have the longest wavelenght of absorption. wavelength is inverse of energy. Conjugation decreases the energy that is higher the conjugation in the system greater would be the wavelegth, hence B) ith 4-bonds in conjugation as opposed to 3 in A), C) and D) would have he longest wavelength.

5. Of the given statements,

D) Formation of the two products arises from a common resonance stabilized carbocation intermediate

is the true statement. The kinetic products is obtained at low temperatures whereas, the thermodynamic product is obtained at high temperatures.

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