[ksack001]

Does anyone remember how to do the integration H NMR by hand I forgot I took organic years ago now im taking a structure determination lab and I forgot how to do that and to calculate coupling constants

[alexjaco]

For coupling constants, I believe you have to have the Hertz values and you can figure out the J value from these numbers.

[ksack001]

Ok now does anyone remember how to do the intergration of the peaks with a ruler by hand?

[James Newby]

Find a peak you know corresponds to part of your molecule and measure the integration line with a ruler. In my experiments i use a tButyl group so i know the integration line length of these groups is equal to 9 hydrogens.  Divide the length of the line by the number of hydrogens to get the value of 1 hydrogen.  All your other peaks line values should be relative to this value.

[ksack001]

I still dont get it. I have 5 peak I thought I picked the smallest one measure it and then compare it the the other integration lines and determine that number of hydrogens from there. This is so simple I remember doing this like nothing back in the day now im lost

[ksack001]

I am given the formula, the spectrum of the H NMR, and it has the integration lines with no values on the lines I have to measure by hand and then I am to determine the structure. Obviously I calculate the IHDs first. THen I know a CH2 for example will split other protons into a triplet and all that, multiplicity. I cant do the integration which would help in determing these structures faster which I cant figure out how to do wow its amazing how you forget something in an mear 4 semester and then I have to calculate coupling constants

[ksack001]

Nevermind i figured out the integration duhhhh!!!. But the coupling constants still I am dont fully understand

[James Newby]

I am not that strong on coupling constants but i will give you my limited knowledge! Firstly understand what environment the protons are in, there is nothing worse than guessing what you are seeing.  If there is a triplet measure from the middle of the central peak to the middle of the external peaks.  The two J values will be the same.  If you want to convert between cm and Hertz there is a conversion chart on the NMR printout.

It gets more complicated when the proton(s) are coupling to more than one environment.  If you need help on that i need to know what the splitting pattern is.

[Med90]

To calculate coupling constants, it will be easier if you have Hz values instead of ppm. For e.g if you have doublet then just substract two Hz values you will get the Coupling constants (J value)
If you have tirplet, substract middle one with either of the peak, in all most all cases both values should be equal
If you want to find out using ppm, then you can just substract lower value with higher one and multiply it with your NMR system value in MHz.(like 250 MHz, 300 , 600)

Hope it will be helpful.

<a href="http://www.medchemblog.blogspot.com">Medchemblog</a>

[tbuihuu]

These works will be easier when u see on a spectrum.