_Infra-Red (IR)- Nuclear Magnetic Resonance (NMR)

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Chemistry

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Feb 20, 2024

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Lab 1 Report : Infra-Red (IR)- Nuclear Magnetic Resonance (NMR) Exercises In Molecular Spectrosc opy- Structural Determination Chem 2425 Prof: Dr. Cherif

Introduction: The purpose of these two techniques is to identify an organic compound's structure. When it comes to revealing whether or not particular functional groups are present, IR ( Infrared Spectroscopy) is most helpful. When comparing samples, IR can produce a molecular fingerprint that can be utilized. Two pure samples may be considered to be the same compound if their infrared spectra match. Nuclear Magnetic Resonance (NMR) spectroscopy is used to analyze and present data regarding the structure and composition of molecules. Although each of the options is somewhat relevant, the most accurate response is that NMR spectroscopy makes it possible to identify a compound's carbon-hydrogen framework. Experiment Procedure: In this case problems 8, 9, and 10 were assigned so, use the following spectrums to identify the structure of each compound in the text or any other organic text study text.First calculate degree of unsaturation by using the following formula: 1 + c - ½ ( H-X+N). Compounds can be distinguished using IR spectroscopy according to the bond vibrations in each one. mostly done by shining a broad-spectrum light source onto the sample through an interferometer, which blocks all but a few wavelengths of light at a time. The light intensities for every interferometer setting are measured by an infrared detector. In order to find what functional groups are the spectrum showing it’s necessary to check the table and observe the absorption range which is the wavenumber, and the intensity percentage. Once the functional group was found, move to the NMR, and find each type's 1H NMR chemical shift in the spectrum. Chemical shift, which indicates a signal's location on the NMR spectrum, is measured in parts per million (ppm). It represents the electronic surrounding field of the NMR-active nuclei. Numerous elements, including hybridization, adjacent atoms, and electronegativity, affect the chemical shift. Additional information can be obtained from the shape of peaks. Broad peaks, for instance, can be a sign of dynamic molecular processes or exchangeable protons. The NMR will tell how many CH3, CH2, CH and which one is single, double, triple, quadrant, or multiple.The molecule and it will also confirm if the molecule is alcohol, alkyl, vinylic, halogen, etc. Once it was determined how many CH3, CH2, or CH are in the molecule the only thing left is to join all those molecules just like if it was a puzzle.

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Like it was mentioned before problems 8, 9, and 10 were assigned. For problem 8 the molecule was C 8 H 14 O and the first thing is to find the degree of unsaturation which is 2, by knowing that the D.U is 2 there is a possibility that there is 2 double bond, 1 double bond and 1 ring, 2 rings, or 1 triple bond. By looking at the IR The C(sp3)-H tension bands are located at 2988, 2819, and 2800 cm-1. One can attribute the tension band at 1718 cm-1 to C=O (ketone). , and the NMR is showing that there are 3 CH3, 2 CH2, one carbonyl, and one vinylic. It also shows there are 2 m, 1 t, 1 S, and 1 D. The draw is in problem 8 next to the spectrums. Degree of unsaturation for problem 9 is 0, so that means there is no double bond, triple bond or a ring, just sigma bonds. The IR shows that there is an alkane group at 2978 cm-1.In the NMR 3 H splits into three due to a 2:1 ratio at 1.0 ppm. The 1.7-point peak suggests doubling (d). multiples (m) are obtained for the peak at 1.8 and the peak at 4.1 ppm. The NMR shows there are 2 CH3, 1 CH2, 1 CH, and 1 halogen which in this case is Br. The molecule is CH3CH(BR)CH2CH3. For problem 10, degree of unsaturation is 4, and the IR shows that there is an alcohol, the NMR shows a anaromatic, an alcohol, 3 methyls, and a benzyl group. Conclusion: NMR and IR Spectroscopic techniques offer valuable insights into the composition of organic compounds. Absorption spectroscopy is a technique used to investigate how molecules interact with electromagnetic radiation. Absorption at a specific frequency is often indicative of the presence of a particular structural unit in the molecule. Spectroscopy is useful because it can be completed quickly and without causing damage. After research, the sample might be recovered. Each spectrum typically contains a large amount of structural information and just a small quantity is needed. Organic chemists frequently employ the ultraviolet (UV), infrared (IR), and nuclear magnetic resonance (NMR) spectra to get structural information.