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Topic: Figuring out rings  (Read 5310 times)

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jena

  • Guest
Figuring out rings
« on: February 15, 2005, 02:56:27 PM »
Could someone please help me with this question:

A compound with a molecular forumula of C13H19BrO has at most how may rings?

My answer is four, using this forumula:

# of Rings= 1+#C-(#H+#X)/2 + (#B+#N)/2

#C-Carbons
#H-Hydrogens
#X-Halogens
#B-Boron
#N-Nitrogen

Please help and Thank You :)

dexangeles

  • Guest
Re:Figuring out rings
« Reply #1 on: February 16, 2005, 12:40:18 AM »
this is how i do it

alkanes are normally CnH2n+2
so that makes (13 x 2) + 2 = 28 supposed hydrogens for an alkane
your molecule only has 19 so ---> 28 - 19 = 9 hydrogens less
we know a double bond reduces an alkane by 2 electrons -- alkenes are CnH2n
and we know that a ring constitutes (is like) a double bond in this manner
so you possibly have 4 double bonds, or four rings
(not including triple bonds and others) just making the explanation as simple as possible

in short all I do is get the max possible Hs by (13 x 2) + 2 = 28
deduct that by what the molecule has 28 - 19 = 9
divide it by two -- 9/2 = 4.5
that gives you 4 possible double bonds

if there are other methods, i'm all ears too :)



jena

  • Guest
Re:Figuring out rings
« Reply #2 on: February 16, 2005, 03:37:40 PM »
So how do you figure in the extra's that are nitrogen or boron based off the formula that I used previously.

Thank you  :)

dexangeles

  • Guest
Re:Figuring out rings
« Reply #3 on: February 17, 2005, 12:25:57 AM »
it just tells me what the max possible is, then i go to H-NMR, C13 NMR, FTIR
« Last Edit: February 17, 2005, 12:26:52 AM by DA »

jena

  • Guest
Re:Figuring out rings
« Reply #4 on: February 17, 2005, 05:59:47 PM »
Hi,

Sorry but I don't understand what you mean by H-NMR, C13 NMR, FTIR  ???

Again, how do you figure in the extra's that are nitrogen or boron?

Please Help  :-\

Thank you :)

dexangeles

  • Guest
Re:Figuring out rings
« Reply #5 on: February 17, 2005, 11:24:45 PM »
each molecular formula can give you a lot of different molecular configurations, so you can't really figure out the structure by just looking at it.  That's when FTIR and NMR helps.  I think this site has a link to explanations of FTIR and NMR.  We need to ask Mitch

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