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Topic: I'm not sure how to go about doing this  (Read 474 times)

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Offline StaticPoptart

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I'm not sure how to go about doing this
« on: June 04, 2020, 01:26:35 PM »
1.   (a) Consider the chemotherapy drug (1) shown below.
(1200px-Taxol.svg.png)
(i)   Circle and label five different oxygen-containing functional groups present.     
For this I found amide, alcohol, ester, ketone, ether, but I'm not sure if there are more 
 
(ii)   Identify ALL the chiral centres present in compound (1) with a star *.      
I found 1 with the alcohol group attached to the amide group, and another on the ring next to the ester structure to the right of the first one. I'm not sure of there are more

(iii)   Select ANY ONE of the chiral centres you have identified in part (ii) above, label with a letter Z and assign the correct Cahn-Ingold-Prelog (R, S) configuration. In your answer include the assignment of priorities.
i used the first chiral center and I got S.                  

(b) The following heterocyclic compound (2) is currently being evaluated in numerous clinical trials to
    investigate its potential as a possible treatment for COVID-19. Using your knowledge and the
    criteria for aromaticity in your response, determine and discuss if the compound is aromatic, non-
    aromatic or anti-aromatic.               
(unknown.png)
Using Hukel's rule, i got the structure as non aromatic since it didnt follow the rule, but I may have missed a Pi electron

(c) For the following chemical species (3), draw all the resonance structures that are possible using
      appropriate diagrams and curved arrows to show the movement of electrons.
(pics.png)
I have trouble with this so I'm not sure how to do this.

(d) In one of your chemistry laboratory exercises, you were asked to perform a hydrohalogenation reaction with starting material A and HCl. Instead of producing the product you expected, B, you obtained a mixture of two products B and C in unequal amounts of which C was formed in a much higher yield.   
(untitled.png)
(i)   Suggest a detailed reaction mechanism to explain the formation of the unexpected major product C.
(ii)  Concisely explain why this unexpected major product C predominated in your reaction.
No idea here either
« Last Edit: June 04, 2020, 02:05:40 PM by StaticPoptart »

Offline Babcock_Hall

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Re: I'm not sure how to go about doing this
« Reply #1 on: June 04, 2020, 03:40:54 PM »
I found many more than two centers of chirality.  Maybe you could explain how you are judging this.

Regarding the last question, draw the stepwise mechanism, and something may occur to you.

Offline StaticPoptart

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Re: I'm not sure how to go about doing this
« Reply #2 on: June 04, 2020, 03:49:29 PM »
For the chiral center I'm judging it by being 4 different groups attached to 1 C. Most of the options i think that are chiral centers have of the same groups, however, i can be wrong with it.

As for the second part, I don't actually have notes on it, but i assume that from stability of the ring, the Cl being directly attached is more stable and then more likely to be formed. As for reaction mechanism I'm not sure how to do that
For the resonance part, I've been doing some work for that and i think that there are 4 possible structures that can be formed, the one that is given, one where the =O is on the lower C in that ring, and 2 where there is a double bond formed between each of the CH3s
« Last Edit: June 04, 2020, 04:00:06 PM by StaticPoptart »

Offline Babcock_Hall

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Re: I'm not sure how to go about doing this
« Reply #3 on: June 04, 2020, 05:45:35 PM »
When HCl adds to an alkene, it does not do so in a single step but instead the proton adds first and then chloride adds in a subsequent step.  In other words the reaction proceeds through a discrete intermediate.  Your class notes or textbook will help (this is common first-semester organic chemistry).  You have to be able to draw this intermediate to understand how C is formed in preference to B.  It is not closely related to the stability of the ring.

With respect to resonance, please show your drawing.  You may be suggesting a structure that violates the octet rule; if so, then you can be sure that it is not a correct answer.  What can we say is generally true about atoms that participate in resonance?

With respect to centers of chirality, let me make a general example.  Suppose there is a carbon that is bonded to H, OH, and to two other carbons.  Is this carbon a center of chirality?  It depends on the groups bonded to the two carbons. If both carbons are methyl groups then carbon-2 is not a center of chirality.  If one carbon is a methyl group and one carbon is an ethyl group, then carbon-2 is a center of chirality.

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