Thermodynamics and Thermochemistry - Result Question 69

####69. When 1-pentyne $(A)$ is treated with $4 N$ alcoholic $KOH$ at $175^{\circ} C$, it is converted slowly into an equilibrium mixture of $1.3 %$ 1-pentyne $(A), 95.2 % \quad 2$-pentyne $(B)$ and $3.5 %$ of 1, 2-pentadiene $(C)$. The equilibrium was maintained at $175^{\circ} C$. Calculate $\Delta G^{\circ}$ for the following equilibria.

$$ \begin{array}{lll} B \rightleftharpoons A, & \Delta G^{\circ}{ } _1=\text { ? } \ B \rightleftharpoons C, & \Delta G^{\circ}{ } _2=\text { ? } \end{array} $$

From the calculated value of $\Delta G^{\circ}{ } _1$ and $\Delta G^{\circ}{ } _2$ indicate the order of stability of $(A),(B)$ and $(C)$. Write a reasonable reaction mechanism showing all intermediates leading to $(A),(B)$ and $(C)$.

(2001, 10M)

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Solution:

  1. At equilibrium : $B \rightleftharpoons A$

$$ \begin{array}{cc}



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