{"id":890,"date":"2018-01-14T15:12:29","date_gmt":"2018-01-14T15:12:29","guid":{"rendered":"https:\/\/www.studyorgo.com\/blog\/?p=890"},"modified":"2018-01-14T15:12:29","modified_gmt":"2018-01-14T15:12:29","slug":"ir-spectroscopy-review","status":"publish","type":"post","link":"https:\/\/www.studyorgo.com\/blog\/ir-spectroscopy-review\/","title":{"rendered":"IR Spectroscopy Review"},"content":{"rendered":"

Studying ahead\u00a0for Organic Chemistry<\/a> this Spring semester is a good\u00a0way\u00a0for getting the best grade this semester and keeping up with the rigorous course work in Orgo 2.\u00a0 Most students find the pace of this class very challenging\u00a0compared to other courses.\u00a0 This is because while there is a lot of information to learn, it also builds on previous concepts from Orgo 1, a course most students want to forget!\u00a0 In your time before classes begin, consider reading ahead or brushing up on some concepts that were covered late last semester to give you a boost right away.<\/p>\n

But don\u2019t worry!\u00a0 StudyOrgo<\/a> has you covered.\u00a0 Our Editors have spent years tutoring and teaching Organic Chemistry to students and we have seen all of the pitfalls common to the first few weeks of the semester.\u00a0 Our online platform allows members to learn organic chemistry concepts and mechanisms quickly and the material presented in an easy-to-follow format. Follow along with us and sign up with StudyOrgo<\/a> today to help prepare you for all of your Organic Chemistry questions.<\/p>\n

One of the concepts you will need to have mastered quickly in Orgo 2 is the usefulness of Infrared (IR) Spectrometry.\u00a0 In this article, we will break down the key concepts and give you all the info you need to master this technique quickly.<\/p>\n

IR Spectroscopy Principles<\/strong><\/p>\n

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A usefulness of using light for analysis is it is relatively non-destructive and cheap to produce.\u00a0 We can see that there are many regions of electromagnetic radiation that we can use for molecular predictions.\u00a0 For instance, long wavelengths like microwaves are used in NMR for determining atomic structure.\u00a0 Longer wavelengths like IR and UV\/Vis region are used for predicting functional groups and can help you identify unknown compounds.\"\"<\/a><\/p>\n

Infrared radiation causes vibrating the bonds between atoms.\u00a0 This is a similar principle to how heating up molecules works, and you may have heard of infrared imaging systems, which can measure the relative temperature of molecules.\u00a0 This technology works on a similar principle to IR spectroscopy, but we use it in the lab to determine functional groups.<\/p>\n

Higher energy regions of the IR spectrum (larger wavenumbers) will cause stretching<\/strong> of bonds where lower energy regions (smaller wavenumbers) will cause bending and twisting<\/strong>.\u00a0 Thus, depending on the type of bond and the atoms involved in the bond, we can predict what they are based on which wavenumber region they absorb.<\/p>\n

There are 3 pieces of information you can get from the IR spectrum of samples.<\/strong><\/p>\n

Signal Region<\/strong><\/em>\"\"<\/a><\/p>\n

In the graph above, we can see the IR spectrum for isopropanol.\u00a0 We see that the range of wavenumbers (inversely proportional to wavelength), there are multiple regions that are causing unqiue-looking signals.\u00a0 The functional groups are alkane and alcohol.\u00a0 Almost all your moleucles will have C-C and C-H bonds, so many o fhtese signals are not useful.\u00a0 But an alcohol is unqiue, with a large peak at 3400.<\/p>\n

Signal Intensity<\/strong><\/em>\"\"<\/a><\/strong>Some signals will be weak and some will be strong, as we see in the figure above.\u00a0 This has to do with how efficiently the region is being absorbed by the molecule.\u00a0 If it is a strong signal it should be consistent and easy to detect.\u00a0 However some bonds are not as efficient.\u00a0 With these signals, sometimes you miss them because they are too weak.\u00a0 So if you think you may have a functional group but the peak is not there, remember it maybe \u201cinvisible\u201d if it is a weak signal.\u00a0<\/strong><\/p>\n

Signal Shape<\/strong>\"\"<\/a>Most types of bonds will absorb in a very narrow region of the IR, giving the typical narrow signal <\/strong>shape. Only a few types of bonds will case large regions of the spectrum to absorb, causes a broad signal<\/strong>.\u00a0 These always are functional groups that can undergo hydrogen bonding, such as O-H, N-H, C=O, etc.\u00a0 Typcially OH and COOH functional groups are very broad, while carbonyls are amines are more broad than ususal.<\/p>\n

Common signals used to predict functional groups<\/strong><\/em><\/p>\n

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Analytical Chemistry – Infrared (IR) Spectroscopy<\/a><\/p><\/blockquote>\n