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A hydrocarbon (A) of molecular weight 54 reacts with an excess of Br_2 in CCl_4 to give a compound (B) whose molecular weight is 593% more than that of (A). However, on catalytic hydrogenation with excess of hyrogen (A) forms (C) whose molecular weight is noly 7.4% more that that of (A). (A) reacts with CH_3CH_2Br in the presence of NaNH_2 to give another hydrocarbon (D) which on ozonolyisis yields kiketone (E). (E) on oxidation gives propionic acid. Give the structure of (A) to (E) with reason.

Answer» <html><body><p></p>Solution :step 1. to determine the molecular weights of <a href="https://interviewquestions.tuteehub.com/tag/compounds-927010" style="font-weight:bold;" target="_blank" title="Click to know more about COMPOUNDS">COMPOUNDS</a> (B) and (C) <br/> (i). The molecular weight of compound (A) is 54 while that of compound (B), which it <a href="https://interviewquestions.tuteehub.com/tag/gives-1007647" style="font-weight:bold;" target="_blank" title="Click to know more about GIVES">GIVES</a> on treatment with an excess of `Br_2` in `C Cl_4`, is `593%` more than that of (A). <br/> Molecular weight of `(B)=((100+593))/(100)xx54=374.22` <br/> Thus the increase in weight due to the adiiton of Br atoms is `374.22-54.0=320.22` <br/> Since atomic weight of Br is 80, the number of Br atoms added `=(320.22)/(80)=4`. As such the <a href="https://interviewquestions.tuteehub.com/tag/hydrocarbon-1034072" style="font-weight:bold;" target="_blank" title="Click to know more about HYDROCARBON">HYDROCARBON</a> (A) must be an alkyne. <br/> (ii). Further since the molecular weight of compound (C) which hydrocarbon (A) gives on catalytic <a href="https://interviewquestions.tuteehub.com/tag/hydrogenation-493186" style="font-weight:bold;" target="_blank" title="Click to know more about HYDROGENATION">HYDROGENATION</a>, is only `7.4%` more than that of (A). The molecular weight of (C) is <br/> `((100+7.4)xx54)/(100)=57.994=58`(approx) <br/> Thus, the increase in weight due to the addition of H atoms `=58-54=4`. <br/> Since the atomic weight of `H` is 1 the number of H atoms added during catalytic hydrogenation is `(4)/(1)=4`. Therefore, hyrocarbon (A) must be an alkyne. <br/> <img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/KSV_P1_C02_S01_019_S01.png" width="80%"/> <br/> <img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/KSV_P1_C02_S01_019_S02.png" width="80%"/></body></html>


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