Q4P - Organic Chemistry (Mcmurry)

Question

The following NMR peaks were recorded on a spectrometer operating at

200 MHz. Convert each into O¹ units.

(a) CH₃CI; 1454Hz  

(b)  CHCI₃; 610Hz  

(c)  CH₃OH; 693Hz

(d)   CH₂CI₂; 1060Hz  

Step-by-Step Solution

Answer

(a)The value of $\delta$ for CHCI₃ is 7.27.

(b) The value of $\mathrm{\delta }$ for CH₃CI  is 3.05.

(c) The value of $\mathrm{\delta }$ for CH₃OH is 3.46.

(d) The value of $\mathrm{\delta }$for is CH₂CI₂  5.30.

Step 1: NMR spectroscopy

Nuclear magnetic resonance (NMR) spectroscopy constitutes a spectroscopic technique used to identify the structure of a particular molecule. A particular molecule’s carbon-hydrogen framework can be mapped using this technique. Several techniques like NMR, Mass and IR are combined to obtain the structure of even complex molecules. 

Step 2: Converting the given frequency into σ units in option (a)

(a)The observed chemical shift is 1454Hz .

The operating frequency of the ₁H NMR is 200 MHz .

The value of δ can be found as:

Hence, the value of $\mathrm{\delta }$is 7.27. 

Step 3: Converting the given frequency into δ units in option (b)

(b) The observed chemical shift is 610Hz .

The operating frequency of the ¹H NMR is 200 MHz .

The value of can be found as:

Hence, the value of $\mathrm{\delta }$is 3.46. 

Step 4: Converting the given frequency into σ units in option (d)

(d) The observed chemical shift is 1060 Hz.

The operating frequency of the ¹H NMR is 200 MHz.

The value of δ can be found as:

Hence, the value of $\mathrm{\delta }$ is 5.30.