山东大学：《物理化学》课程教学资源（讲义资料）10.7 Methods for Studying fast reactions

810.7 Methods for Studying fast reactions Levine: pp 569-572 17.14 Fast reactions

§10.7 Methods for Studying fast reactions Levine: pp. 569-572. 17.14 Fast reactions

8 10.7 Study of fast reactions 10.7.1 Basic consideration What is fast reaction? a fast reaction is that can proceed very fast and complete in less than few seconds Examples: Neutralization reaction, explosion reaction and recombination reaction of radicals Basic characteristics: 1)The activation energy of fast reaction is usually less than 40 kJ mol-l and with k s high as 10 dm mol-s- (2) This kind of reaction is difficult to study using ordinary methods

What is fast reaction? A fast reaction is that can proceed very fast and complete in less than few seconds. Basic characteristics: (1) The activation energy of fast reaction is usually less than 40 kJ mol -1 and with k as high as 1011 dm3 mol-1 s -1 . (2) This kind of reaction is difficult to study using ordinary methods. Examples: Neutralization reaction, explosion reaction and recombination reaction of radicals §10.7 Study of fast reactions 10.7.1 Basic consideration:

8 10.7 Study of fast reactions 10.7.1 Basic consideration Methods for measuring reaction rate The physical parameters usually used for monitoring reaction process includes volume, pressure, electric conductance, pH, refractive index, thermal conductivity, polarimetry, spectrometry, chromatography, etc. 1)Real time analysis 1)Static method Quenching Analyzing methods 2)Flow method

The physical parameters usually used for monitoring reaction process includes volume, pressure, electric conductance, pH, refractive index, thermal conductivity, polarimetry, spectrometry, chromatography, etc. Analyzing methods: 1) Static method 2) Flow method 1) Real time analysis 2) Quenching Methods for measuring reaction rate §10.7 Study of fast reactions 10.7.1 Basic consideration:

8 10.7 Study of fast reactions 10.7.1 Basic consideration Generator Reaction Detector Methods for recording time msμs—>ns—>ps—>fs

§10.7 Study of fast reactions 10.7.1 Basic consideration: Methods for recording time ms⎯→s ⎯→ns ⎯→ps ⎯→fs Generator Reaction cell Detector

10.7 Reaction rate and rate equation 10.7.2 Continuous flow method Attain a steady-state flow The coordination reaction between Fe2+ and Mixer detector thiocyanate SCN- in aqueous solution Moving direction Stable flow:/o t Distance corresponds to time B v=10 m s-I step of0. 1 mm corresponds to 10 us Measurements are done using a stepwise method

10.7 Reaction rate and rate equation Stable flow: l  t Mixer detector Moving direction A B Attain a steady-state flow: The coordination reaction between Fe2+ and thiocyanate, SCN– , in aqueous solution. Distance corresponds to time v = 10 m s-1 , step of 0.1 mm corresponds to 10 s. Measurements are done using a stepwise method. 10.7.2 Continuous flow method

10.7 Reaction rate and rate equation 10.7.2 Continuous flow method doi:10.1006/mbi2000.4124availableonlineathttp:/www.idealibrary.comonIdEalj.mOlBial.(2000)303,773-795 JMB 几 Multiple-step Kinetic Mechanism of DNA-independent ATP Binding and Hydrolysis by Escherichia coll Replicative Helicase DnaB Protein: Quantitative Analysis Using the Rapid Quench-flow Method Surendran Rajendran, Maria J. Jezewska and Wlodzimierz Bujalowski Difficulty:(1)a large amount of solution is required;(2) steady and exact motion ./ of the detector. 0.05 0.1 0.15 Time(

Difficulty: (1) a large amount of solution is required; (2) steady and exact motion of the detector. 10.7 Reaction rate and rate equation 10.7.2 Continuous flow method

10.7 Reaction rate and rate equation 10.7.3 Stopped-Flow Measurements in real time Fluorescence not requiring large amounts of reagents(as Optical.i. Absorbance Path little as 1 cm3 may be sufficient) the time resolution is a little faster then for Mixer Stopping Syringe continuous flo Fixed probe strategy The usual dead time of a stopped flow apparatus is 1-2 milliseconds but some new devices have been Drive developed that have dead times of 0.3-0.6 ms Single Mixing Stopped-Flow

10.7.3 Stopped-Flow Measurements in real time not requiring large amounts of reagents (as little as 1 cm3 may be sufficient) the time resolution is a little faster then for continuous flow. Fixed probe strategy. The usual dead time of a stopped flow apparatus is 1–2 milliseconds but some new devices have been developed that have dead times of 0.3–0.6 ms 10.7 Reaction rate and rate equation

10.7 Reaction rate and rate equation 10.7.3 Stopped-Flow Stopped flow is set up by Hamilton Hartridge and f.j. W. roughtonIn 1923 https://commons.wikimediaorg/wiki/file:Stopflowapparatusjp

10.7.3 Stopped-Flow https://commons.wikimedia.org/wiki/File:Stop_flow_apparatus.jpg Stopped flow is set up by Hamilton Hartridge and F. J. W. RoughtonIn 1923. 10.7 Reaction rate and rate equation

10.7 Reaction rate and rate equation 10.7.4 Relaxation method Temperature Jump; Pressure jump 12kV Flash/Laser photolysis Path k at Temperature Jump(not to scale) a-x n at

10.7.4 Relaxation method e e e ln ( ) x x k at x x + = − e e e ln ( ) a x x k at x x − − = − Temperature jump; Pressure jump; Flash / Laser photolysis 10.7 Reaction rate and rate equation

10.7 Reaction rate and rate equation 10.7.4 Relaxation method s n 1953 Manfred eigen introduced high-frequency sound waves as a way of bringing about rapid chemical reactions and processes, such as the dissolving of a salt in a solvent. The speed of the reaction calculated based the sound In 1967, Manfred Eigen was awarded, along with Ronald George waves' energy. He also Wreyford Norrish and George Porter, the Nobel Prize in Chemistry. studied how electrical They were distinguished for their studies of extremely fast chemical voltage affects chemical reactions induced in response to very short pulses of energy processes

In 1967, Manfred Eigen was awarded, along with Ronald George Wreyford Norrish and George Porter, the Nobel Prize in Chemistry. They were distinguished for their studies of extremely fast chemical reactions induced in response to very short pulses of energy. 10.7.4 Relaxation method In 1953 Manfred Eigen introduced high-frequency sound waves as a way of bringing about rapid chemical reactions and processes, such as the dissolving of a salt in a solvent. The speed of the reaction could be calculated based the sound waves' energy. He also studied how electrical voltage affects chemical processes 10.7 Reaction rate and rate equation