conversion to compound B (C42H74). How many alkynes does compound A possess Ques

Question

conversion to compound B (C42H74). How many alkynes does compound A possess Question 8 [1.5 pts] An NMR signal has been reported to occur 5310 Hz downfield from TMS. Given that the signal's chemical shift is 11.8 ppm what is the operating frequency of the spectrometer (in MHz)? Enter just the numerical value expressed as a whole number. Don't be alarmed when Canvas adds trailing zeros to the number you type in. This action will not affect the grading of your answer Question 9 11.5 pts] Which one of the following statements is correct? Ho O Proton Hc is more shielded than proton Ho Proton He is less shielded than proton O None of the above Question 10 11.5 pts) Which one of the following statements is correct? O The Ho Hf HE Befiectve sensed by proton He is smaller CI than the Behave sensed by proton HF

Explanation / Answer

Question 8:

Frequency of the signal = 5310 Hz

Frequency of the reference, TMS = 0 Hz

Chemical shift= 11.8 ppm

Chemical shift, = (position of signal – position of reference peak) * 106/ spectrometer frequency

11.8 ppm = (5310 Hz – 0 Hz) * 106/ spectrometer frequency

        Therefore, spectrometer frequency = (5310 Hz – 0 Hz) * 106/11.8

                                                  Spectrometer frequency = 450 106 Hz = 450 MHz

Question 9:

Proton HC is more shielded than HD, as the latter is comparatively closer to the aldehyde group (electron withdrawing group).

Electron withdrawing groups will deshield the protons.

Question 10:

The magnetic field at the nucleus is altered from B0 to a quantity B0(1-s) where s is called the shielding constant.

Greater the electron density around the nucleus, higher the opposing magnetic field to B0 from the electrons, the greater the shielding. Thus proton experiences lower external magnetic field (B effective).

If the electron density around a nucleus decreases, opposing magnetic field becomes small and therefore, the nucleus feels more the external magnetic field B0, and therefore it is said to be deshielded. Because the proton experiences higher external magnetic field

Higher the shielding, lower the B effective.

Thus, The B effective sensed by the proton HF is more, as it comparatively closer to the chloride groups than HE

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