A compound A with molecular formula C 20 H 20 ClBrFN 5 O 3 S is hydrogenated to
ID: 888439 • Letter: A
Question
A compound A with molecular formula C20H20ClBrFN5O3S is hydrogenated to give a compound B with molecular formula C20H36ClBrFN5O3S. How many rings does compound A have? Assume that sulfur in this case has a valency (not valence electrons) of 4 in these molecules and that all other atoms have standard valencies.
4 b. 3 c. 2 d. 1 e. not a.-d.
How many total bonds does compound B have?
74 b. 73 c. 72 d. 71 e. not a.-d.
So I am having a problem figuring out how to get the total bonds of this compound and also how to get rings+pi. I know through hydrogenation there are 8pi bonds. Now if I do the equation for rings+pi for the hydrogenated compound there will be no pi bonds so I will get the number of rings but I am not sure if I minus or add for the sulfur, if I add for the sufur I get 5 rings, if I minus I get 3 rings. So this is making the second question complicated because if I go with 3 rings, the answer is 70, but if I go with 5 rings it ends up being 72. The relavent equations are below:
Rings+pi= 1 + C + N/2 - H/2 - X/2 = 1 + S (valency of element Y - 2)/2 Y (This is where I know sulfur would be (4-2)/2 which gives 1 so it will count in the equation as only itself however I am not still for the adding or substracting of it.
Now for compound B since if it after hydrogenation we know there is ONLY sigma bonds, so we can use SIGMA= (The summation[addition])of all atoms in the molecule +rings -1
So please help me, I am on the write track just I need to know just one part to put it all together!
Explanation / Answer
You have to assume the S as if where an additional C (both with valence 4) . So the formula transforms into Rings+pi= 1 + (C +1) + N/2 - H/2 - X/2. So the number of rings is 5 and the total bonds 72.
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