Chemistry Lab Report Example | Topics and Well Written Essays - 2250 words

Chemistry - Lab Report Example These values also imply that the reaction is pseudo first order reaction. (iv) A plot of rate of reaction (J) vs. concentration of AsO33- i.e.[A] was made (figure 2, below). A linear trendline was drawn using MS excel. Slope of this plot gives the rate constant. The value of the rate constant is 5.3x10-3s. d) From data given in table (2) a plot of lnkR' vs. 1/T was made (figure 3, below). Slope of this curve equals -E/R, where E is activation energy of the reaction and R is the Universal gas constant, which equals 8.38 Jmol-1K-1. Therefore, -E/R = 8122.6 K Or, E = 8122.6*8.38 Jmol-1= 68067.4 Jmol-168.7 k Jmol-1 Q3. a) The mechanism in this case is SN1 i.e. Nucleophilic Substitution of First Order. In this mechanism the carbonium ion forms first, to which the nucleofile OH- gets attached in no time. Because formation of carbocation is the slow or rate controlling step therefore this is a first order reaction. Therefore, rate of this reaction is proportional to concentration of hexan-3-ol. Because, carbocation is planer therefore, the nucleofile (OH-) has equal probability of attaching to it from both sides (above as well as below) of the plane. Thus, a mixture of both the optical isomers (R-isomer and S-isomer) forms in equal proportions. The mechanism is shown below: b) (i) In this case S-isomer will form. (ii) The mechanism in this case is SN2 i.e. Nucleophilic Substitution of Second Order. In this case both molecules R-3-bromohexane and NaOH are involved in the reaction mechanism. The nucleofile OH- attacks the positively polarized carbon atom from the other side of the leaving group i.e. from other side of the C-Br bond, because of steric hindrance. This backside attack by the nucleofile...1/T was made (figure 3, below). Slope of this curve equals -E/R, where E is activation energy of the reaction and R is the Universal gas constant, which equals 8.38 Jmol-1K-1. Q3. a) The mechanism in this case is SN1 i.e. Nucleophilic Substitution of First Order. In this mechanism the carbonium ion forms first, to which the nucleofile OH- gets attached in no time. Because formation of carbocation is the slow or rate controlling step therefore this is a first order reaction. Therefore, rate of this reaction is proportional to concentration of hexan-3-ol. Because, carbocation is planer therefore, the nucleofile (OH-) has equal probability of attaching to it from both sides (above as well as below) of the plane. Thus, a mixture of both the optical isomers (R-isomer and S-isomer) forms in equal proportions. The mechanism is shown below: (ii) The mechanism in this case is SN2 i.e. Nucleophilic Substitution of Second Order. In this case both molecules R-3-bromohexane and NaOH are involved in the reaction mechanism. The nucleofile OH- attacks the positively polarized carbon atom from the other side of the leaving group i.e. from other side of the C-Br bond, because of steric hindrance. This backside attack by the nucleofile leads to inversion of the stereo configuration of the molecule. The reaction mechanism is shown below: c) This is because, in the beginning, when the reaction is being carried out in pure water, the