Lecture 7 Infrared Spectroscopy

2y ago
11 Views
2 Downloads
2.23 MB
27 Pages
Last View : 10d ago
Last Download : 2m ago
Upload by : Kian Swinton
Transcription

Lecture 7Infrared spectroscopyFebruary 12, 2019Chemistry 328N

First Midterm Exam 2/20When: Wednesday,When: 7-9 PM (please do not be late)Where: Painter 3.02!!!What: Covers material through Thursday’s lectureRemember: Homework problems!!Practice: Old exams are posted on the web sitePlease bring pencils, an eraser and a calculator onlyand no phones .Do a good job!!!Chemistry 328N

Early Exam Announcement Early Exam on 2/20 @ 5- 7PM in FNT 1.104 Prior approval is required to take the exam early Note that the doors to FNT lock automatically at 5PMYou MUST be on time and need to stay for the durationof the exam. You may not exit the exam room before 7PM No Office Hours will be held on the day after the mid-termexams. (@/21, 3/28, 4/25Chemistry 328N

Mr Hooke says: The position (frequency) of the absorption of astretching vibration depends on– the strength of the vibrating bond (direct) and– the masses of the atoms (inverse) The stronger the bond and the lighter the atomsconnected by that bond, the higher thefrequency (wavenumber) of the vibration The intensity of absorption depends primarilyon the polarity of the vibrating bondChemistry 328N

The energy of electromagnetic radiationc luluu 1l (nu-bar) represents wavenumber, thenumber of wavelengths in 1 cm This is a unit of frequency! units are 1/cm or cm-1 (Kaysers)E hn hcl hc10 microns (micrometers) 1000 cm-1Chemistry 328N

Infrared Absorption FrequenciesStretching vibrations (multiple bonds)Structral unitFrequency, istry 328N

IR Group Correlation TablesChemistry 328N

IR Group Correlation Tables Characteristic IR absorptions for some of thefunctional groups we deal with most oftenBondFrequency (cm-1)O-H3200-3650strong and broadN-H3100-35002850-3300mediumC-HC OC CC-OIntensity1630-18101600-1680medium to strongstrongweak1050-1250strongChemistry 328N

Hydrocarbon VibrationAlkanestretchingC-HCH 2bendingbendingCH 3AlkeneC-HC CAlkyneC-HC CFrequency(cm -1)Intensity2850 - 3000 strong1450medium1375 and 1450 weak to mediumstretchingstretching3000 - 31001600 - 1680weak to mediumweak to mediumstretchingstretching33002100-2250medium to strongweakChemistry 328N

Chemistry 328N

Fingerprint regionChemistry 328N

Chemistry 328N

IRInfrared spectroscopyChemistry 328N

Summary IR measures vibrational transitionsCan be described by classical oscillator theory– Frequency proportional to [ bond strength/mass]1/2 Characteristic Group Frequencies– OH and C O are particularly easy to identify Know how to read the chart cm-1?Practice at the online sites nmr, IR.Excellent!!Chemistry 328N

Chemistry 328N

Practice Problems & Tutorials r-spectra-practice txtjml/questions/Spectroscopy/irmsprb/infrared.htm https://webspectra.chem.ucla.edu/ nic/mc/vol8/mcquestions317h.htm ir-spectroscopy-some-simple-practice-problems/ txtjml/spectrpy/infrared/infrared.htmChemistry 328N

UV-visible SpectroscopyChemistry 328N

UV/Visible Spectroscopy Most UV/visible spectrophotometers cover from– 200 to 400 nm (the near ultraviolet) and– 400 nm (violet light) to 700 nm (red light)Region t200-40071.5 - 143visible400-70040.9 - 71.5C-C bond Disassociation energy 95Kcal/molChemistry 328N

UV/Vis SpectroscopylmaxTransmissionUV-Vis spectral data are plotted asabsorbance (A) versus wavelength (nm)Absorbance (A) Wavelength (nm)Chemistry 328N

Chemistry 328N

UV/Vis SpectroscopyTransmission: a quantitative measure of the extent towhich a compound absorbs ultraviolet-visible radiationat a particular wavelengthWhere:I%Transmission (T) IoX100I0 is the intensity radiation incident on the sampleIis the intensity transmitted through the sampleChemistry 328N

UV/Vis Spectroscopy Absorbance: a quantitative measure of theextent to which a compound absorbs ultravioletvisible radiation at a particular wavelengthAbsorbance (A) logIoIWhere:I0 is the intensity radiation incident on the sampleI is the intensity transmitted through the sampleChemistry 328N

Beer-Lambert law Beer-Lambert law: the relationshipbetween absorbance, concentration, andlength of the sample tubeBeer-Lambert Law: A c lA absorbancec concentration (mol liter -1 )l length of the sample tube (cm) molar absorptivity (liter mol-1 cm -1 ).Experimental values of range from 0 to 106Chemistry 328N

Some Quantitative RelationshipsPlease read: Pages 904-908I%Transmission (T) IoAbsorbance (A) logX100IoIBeer-Lambert Law: A clChemistry 328N

Origin of UV-Vis Absorbance - MO Theory“sigma” bondconservationof orbitalsDE 65 Kcal/moleChemistry 328N

AntibondingBondingChemistry 328N

Chemistry 328N

UV/Vis Spectroscopy Transmission: a quantitative measure of the extent to which a compound absorbs ultraviolet-visible radiation at a particular wavelength Where: I 0 is the intensity radiation incident on the sample I is the intensity trans

Related Documents:

1. Introduction to Spectroscopy, 3rd Edn, Pavia & Lampman 2. Organic Spectroscopy – P S Kalsi Department of Chemistry, IIT(ISM) Dhanbad Common types? Fluorescence Spectroscopy. X-ray spectroscopy and crystallography Flame spectroscopy a) Atomic emission spectroscopy b) Atomic absorption spectroscopy c) Atomic fluorescence spectroscopy

Visible spectroscopy Fluorescence spectroscopy Flame spectroscopy Ultraviolet spectroscopy Infrared spectroscopy X-ray spectroscopy Thermal radiation spectroscopy Detecting and analyzing spectroscopic outputs The goal of all spectroscopic systems is to receive and analyze the radiation absorbed, emitted, .

Introduction of Chemical Reaction Engineering Introduction about Chemical Engineering 0:31:15 0:31:09. Lecture 14 Lecture 15 Lecture 16 Lecture 17 Lecture 18 Lecture 19 Lecture 20 Lecture 21 Lecture 22 Lecture 23 Lecture 24 Lecture 25 Lecture 26 Lecture 27 Lecture 28 Lecture

1 Infrared spectroscopy Chapter content Theory Instrumentation Measurement techniques Mid-infrared (MIR) – Identification of organic compounds – Quantitative analysis – Applications in food analysis Near-infrared (NIR) – Properties of the technique – Applications in food analysis Infrared spectroscopy

and cornetite were studied using a combination of infrared emission spectroscopy, infrared absorp-tion, and Raman spectroscopy. Infrared emission spectra of these minerals were obtained over the temperature range 100 to 1000 C. The infrared spectra of the three minerals are different, in line with differences in crystal struc-ture and .

conventions for infrared spectroscopy and for practical reasons are divided wavelengths of radiation to the area close to (A - NIR - Near infrared) 750-900 nm, medium (B-MIR - Middle infrared) from 1.55 to 1.75 micron and far (C - FIR - Far Infrared), 10.4 to 12.5 micron according to field use. To measure the amount of incident light are used

IR Spectroscopy IR Absorption Spectroscopy Laboratory characterization of minerals and materials Near Normal Reflectance Spectroscopy Laboratory applications for determining both n and k as a function of λ IR Reflectance Spectroscopy. Diffuse Reflectance or Bi -directional Reflectance spectroscopy has both laboratory and remote .

Spectroscopy Beauchamp 1 y:\files\classes\Spectroscopy Book home\1 Spectroscopy Workbook, latest MS full chapter.doc Basics of Mass Spectroscopy The roots of mass spectroscopy (MS) trace back to the early part of the 20th century. In 1911 J.J. Thomson used a primitive form of MS to prove the existence of isotopes with neon-20 and neon-22.