Questions Reaction Kinetiquestionscs

reaction kinetics
of 6
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Related Documents
  Kinetic isotope effect  –  not theory Chain reaction  –  identify the steps Recombination reaction  –  most efficacious third body M Determine the rate law What does the rate of a reaction depend on? Which of the following is not  true about termolecular recombination reactions? Which of the following refinements of Lindemann-Christiansen mechanism is false? What is not true about an activated complex? Who first proposed the idea of collisional activation to form a short lived intermediate, A*? The diffusion-controlled rate constant does not  depend on which of the following? Which of the following statements is false regarding branching in chain reactions?] Which of the following is not true regarding explosions? Which of the following is wrong regarding chain reactions? Which statement on the Kinetic Salt Effect is NOT true? Who first proposed that an excited molecule requires enough energy in the critical vibrational energy level (=activated molecule) so that it can react?  What statement regarding the Stopped Flow technique is FALSE?  A. Its applications include the measurement of enzyme kinetics, study of drug-binding processes, or determination of protein structures. B.   The reactants are mixed completely very quickly.  C.   The reaction is monitored as a function of time D.   It is suitable for slow reactions.  E.   The method makes use of UV/Vis spectroscopy.  The Stopped Flow technique is used in the case of enzymatic reactions, because they are very fast and they involve short-lived intermediates. Moreover, the method is very helpful since the reactants  –  the substrate and the enzyme  –  are mixed completely in only 1 ms. Consequently, the method is appropriate for the processes mentioned in A. Which of the following statements is an improvement that Marcus contributed to the RRK, and thus to the previous Simple Collision Theory? A.   A molecule has several vibrational modes B.   Energy flows randomly between vibrational modes C.   The energy distribution in normal modes of vibration is treated statistically D.   The reaction of an excited molecule occurs when enough energy accumulates in one critical vibrational mode E.   The rotational energy is included The contribution of Rudolph A. Marcus to the RRK is even a greater refinement of the model of collisional excitation. Thus, by contrast with the Hinshelwood and RRK theories, it involves that each vibrational mode is treated explicitly, zero point energies of reactants and activated complex are taken into account and the rotational energy is included, so E is the correct answer. Moreover, another important fact is that these features are in good quantitative agreement with the experiment, while in the RRK, the value of the number of vib. modes had to be adjusted in order to give the best fit to experimental data.  Why does the C=O bond in the β -lactam ring appear on an IR spectrum at a stretching frequency of ~1780 cm -1 , instead of ~1675 cm -1 , as in the case of a normal acyclic amide? A.   The N atom is trigonal planar, and thus it has more sp 2  character B.   The C=O bond is longer than in a normal amide C.   The N atom is more pyrimidal, leading to a shorter C=O bond than in a normal amide D.   β -lactams are particularly stable carbonyl functional groups due to the resonance structure Explanation: It can be noticed from the picture of the amide that the nitrogen atom is trigonal planar, with sp 2  character, causing the C-N bond to be shorter and the C=O bond to be longer and appear at a lower IR frequency, so A and B are both incorrect answers. By contrast, in the case of the β -lactams, the N atom is more pyrimidal and has a more pronounced sp 3  character, instead of sp 2 . As a result, the C-N bond is longer than in a normal amide, while the C=O bond is shorter and stronger. Consequently, it appears at a higher frequency, so C is the right answer . D is also an incorrect answer, since the resonance structure in the β -lactams, represented above, does not contribute to its true structure, as it does in amides. Hence, the amides are particularly stable carbonyl functional groups, while the β -lactams are not.  What component from penicillin G, makes it prone to acid hydrolysis? A.   The free carboxylic acid B.   The sulfur atom C.   The β -lactam ring D.   The N-acyl group The reason why penicillin G is prone to acid hydrolysis is the fact that it contains the β -lactam ring, which is highly reactive. However, if the radical R from the N-acyl chain is bulky or is an EWG, the amide carbonyl oxygen is less nucleophilic, and hence the rate of hydrolysis is greatly reduced. This can be noticed from the mechanism below. What is the product of the following reaction?


Jul 23, 2017

WeCycle June 2014

Jul 23, 2017
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks