11 Absorption of what type of electromagnetic radiation resu

11) Absorption of what type of electromagnetic radiation results in electronic transitions? A) x-rays B) radio waves C) microwaves D) ultraviolet light E) infrared light 16 12) Which of the following is the strongest activating group in electrophilic aromatic substitution reactions? A) -CH CHs B)-CHO C)-CO CH D) -NO E) N(CH) 13) Which of the following compounds absorbs the longest wavelength of UV-visible light? A) (E)-2-butene B) (Z)-2-butene C) 1-hexene D) (Z)-1,3-butadiene E) (E),1,5-hexadiene What descriptive term is applied to the type of diene represented by 1,5-octadiene? 14) A) conjugated diene B) cumulated diene C) isolated diene D) alkynyl diene E) None of selections A-D are correct. 15) Which of the following undergoes an SN2 reaction with sodium methoxide most rapidly? A) PhCH2Br B) Ph:CBr C) PhCH2 CH2B D) PhBr E) PhCH CH CH Br

Solution

12) (E) N(CH₃)₂ will have a +I effect on the ring hence it will increase the electron density in the ring, making it a better nucleophile.

13) (D) A compound with more delocalisation of the pi electrons absorbs a light of more wavelength as the energy gap to the next electronic level is smaller hence lesser energy is required. (D) has conjugation and more number of pi electrons hence it is the correct answer.

14) (C) The two double bonds have a gap of more than two single bonds between them hence they come under isolated diene.

15) (A) Ph is electron withdrawing (-I) hence the closer carbon atom will have more partial positive charge, also the nucleophile is very strong.