CHEM 2211 1st Edition Lecture 7Outline of Last Lecture I. IUPAC systematic naming Outline of Current Lecture I. IR spectrums Current LectureIR Spectrums What is IR spectrum?- It stands for infrared spectroscopy - It is a type of graph we could say , and we use it to identify compounds in organic chemistry - The spectrum is obtained by passing infrared radiation through a compound sample - This results in a plot of the percent transmitted of radiation versus the wavenumber radiation transmitted Bonds- Bonds between atoms stretch and bendStretching- Is a vibration along the line of the bond - It changes the bond length Bending - Is a vibration along the does not occur along the line of the bond - A bending vibration changes the bond angle Infrared radiation has the right range of frequencies to correspond to the stretching and bending of bonds These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- When a molecule is bombarded with infrared radiation at the right frequency for a bond it absorbs the radiation - Depending on the wavenumber of the energy absorbed we can identify what kind of bond it is, by using the spectrum An IR spectrum can be divided into two regions - The functional group region - The fingerprint region The functional group region - Is where the functional groups are mostly absorbed - This is the area from 4000 to 1400 cm-1- This is the area we focus on when using IR spectrums - Even if a molecule had the same functional groups they would show up differently because they would be in different environments The fingerprint region - Is specific to the molecule as a whole - Is it the area from 1400 to 600 cm-1- We do not pay attention to this area at all Functional groups - Functional groups show absorption bands at different ranges of wavelengths on the spectrum o Ketoneso Esterso Amideso AlcoholsTypes of intensities - The wavenumbers tell you where to look for a certain group or bond - But you also need to know what intensity to look for - There are threeo Weako Mediumo Strong- There can be a range to like:o Medium-weako Medium-strongWhen looking from the bottom of a spectrum to the top, the closer the signal is to the bottom the stronger it is. Ex: red= strong signal blue= medium signal black= weak signal Signals can also be broad or sharp the blue circled medium point is also sharp and the green circled point is a broad
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