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Author Topic: need help identifying the product  (Read 1801 times)

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xxdesigulxx

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need help identifying the product
« on: December 09, 2012, 05:11:20 PM »

Hi guys,

I need help identifying the product from the spectra. we did a lab on synthesis of benzyl alcohol(preparing benzyl alcohol from benzyl chloride),

Can some please help me identify the functional groups and the Product using the IR, NMR, and Mass spectrum.

Here are the links :

http://oi50.tinypic.com/5mzrpx.jpg       <-IR spectrum
http://tinypic.com/r/hvo4tj/6               <- mass S
http://tinypic.com/r/2qcnq5x/6             <- HNMR
 
thanks. one more thing the boiling point obtained was 160c!. please help me!. Thank you!
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discodermolide

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Re: need help identifying the product
« Reply #1 on: December 09, 2012, 07:45:36 PM »

What groups have you identified up to now?
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Borek

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Re: need help identifying the product
« Reply #2 on: December 09, 2012, 10:33:54 PM »

You have to show your attempts at solving the question to receive help. This is a forum policy, described in the forum rules.
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xxdesigulxx

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Re: need help identifying the product
« Reply #3 on: December 10, 2012, 01:00:08 AM »

Hi.
 i was able to identify o-h (between 3400-3500), c-h (2800-3000), c-o(1100-1300)I dont know if i am rightIn hnmr the gap describes that there is unknown element present. So how can i use the mass spectrum to finthat? In mass spec. The parent peak is 122.so like is that the molar mass. I dont get it.
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discodermolide

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Re: need help identifying the product
« Reply #4 on: December 10, 2012, 01:56:59 AM »

I do not see an OH stretch in the IR.
The peak at m/e = 91 tells you something. You have the MWt. 122, what fragment could be lost here?
What information can you get from the NMR?
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xxdesigulxx

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Re: need help identifying the product
« Reply #5 on: December 10, 2012, 02:14:54 AM »

91 m/z is the base peak i think it tells you that there is benzyl unit present there. NMR there are 3 peaks so, 3 H present there, but i dont know how i can get the formula from there!:(
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discodermolide

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Re: need help identifying the product
« Reply #6 on: December 10, 2012, 02:28:09 AM »

That's right the m/e at 91 is a benzyl radical cation, this fits with the NMR showing 5 aromatic protons.
So you have C6H5-CH2-unknown-unknown.
So what could the unknowns be, does the loss of 31 in the mass. spec say anything? Along with 2H and 3H in the NMR.
Have a guess.

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xxdesigulxx

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Re: need help identifying the product
« Reply #7 on: December 10, 2012, 02:45:12 AM »

is it due to ester?
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discodermolide

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Re: need help identifying the product
« Reply #8 on: December 10, 2012, 02:52:32 AM »

No it is not an ester.
What compounds do you know with a mass of 32?
In the NMR both peaks are singlets. That is no coupling between them. The position of the 2H signal at 4.4 should indicate something to you.

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xxdesigulxx

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Re: need help identifying the product
« Reply #9 on: December 10, 2012, 03:02:32 AM »

oh its sulfur. and the the position of 2h at 4.4 tells us that there is formaldehyde, ch2o present. am i right?

Thank you for immediate response. you are a big help. thanks so much!:)
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discodermolide

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Re: need help identifying the product
« Reply #10 on: December 10, 2012, 03:13:22 AM »

No it is not sulphur, it is an organic fragment.
Formaldehyde is not present it is though CH2O.
So we have C6H5CH2O-unknown. The unknown part has 3 protons in it.
add up the mass of C6H5CH2O and see what is left.
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xxdesigulxx

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Re: need help identifying the product
« Reply #11 on: December 10, 2012, 03:28:33 AM »

the mass of that comes up to 107. so 122-107=15.
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xxdesigulxx

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Re: need help identifying the product
« Reply #12 on: December 10, 2012, 03:31:25 AM »

lithium is the one that has 3 protons
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discodermolide

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Re: need help identifying the product
« Reply #13 on: December 10, 2012, 03:31:39 AM »

Right, so which organic unit has a mass of 15, knowing that there are 3 protons in that fragment?

Look by protons I mean H atoms, you are looking at a proton NMR
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xxdesigulxx

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Re: need help identifying the product
« Reply #14 on: December 10, 2012, 03:38:31 AM »

i dont get it!:(
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