Organic Chemistry Lab Nuclear Magnetic Resonance (NMR) Spectroscopy, Part I

Post by Ay Ayy on February 7, 2017

I have this question
1. (a) Determine the digital resolution of a 12 ppm proton spectrum collected on a 300 MHz NMR instrument.  Number of data points collected for this spectrum was 1K (1024 bytes). [Hint: On a 300MHz instrument, 1PPM=300Hz]              
(b). What would be the resolution of the above spectrum if 2000 data points were collected?            
C. If we increase the spectral width from 12 to 20 ppm and keep all other acquisition parameters same as in problem 1(a) and collect a proton spectrum, what would be the acquisition time and resolution of the newly acquired proton spectrum?

Post by Kaye Lim on November 30, 2016

I have a question regarding how NMR instrument works. This is what I thought, please check if it is correct.

So there is only 1 MHz value of radio wave applied on the sample (like 42.6 MHz for 1 Tesla magnetic field). That powerful pulse of radiowave excites all nuclei including nuclei of F,N,C as well. Then the radio receiver would tune into a correct MHz value to read the released energy from the nuclei (example, 42.6MHz to read proton nuclei, and other corresponding MHz to read nuclei of other atom type). Is everything above correct?

Thank you!

Post by Tram T on May 4, 2016

For protons on Carbon table at 37:04, Why proton of Methyl is more upfield (more shielded)than methylene and methine proton?

I thought that since alkyl R is EDG, the more alkyl R group like in the case of methine proton, the more electron rich the area thus methine proton would give the most upfield signal instead of proton on methyl.

Please explain! Thank you! Great lecture!

Post by Jeremy Cohen on November 11, 2015

Dr. Starkey, I didn't know where to put this but I just wanted to say thank you for all of your help this semester.  Your lectures have been incredibly helpful in getting me through orgo 1.

Post by Akilah Futch on July 16, 2015

what if you are not given the formula of the structure and all you have is the H nmr.

Post by Anhtuan Tran on July 1, 2014

Hi Dr. Starkey,
When it comes to calculate the chemical shifts for CH2 group, we use the formula: 1.2 + ΔR1 + ΔR2 and we look up the table for the values of Δ. My question is where those values are coming from and how did they calculate those values and what is the difference between the Δ values and the regular values that we use for H that has only one neighbor.
Thank you.

Post by Andrea Cola on January 31, 2014

How many 1H NMR signals would 1,3,5-trimethylbenzene give?

Post by brian loui on April 2, 2013

on example 2, (the one w/ the carbonyl) aren't the "e" methyls diastereotopic and therefore not equivalent? i made models... and they're not superimposable and aren't enantiomers.