Problem 1

In 1956 Huisgen and Ugi obtained the compound

\ce{PhX}

(A), unambiguously confirmed 27 years later by single-crystal X-ray diffraction. In 2001 quantum chemistry predicted the

\ce{FeX2}

molecule (B) with

\ce{Fe^{2+}}

and

2\ce{X-}

binding energy close to the isoelectronic molecule

\ce{FeY2}

(C, discovered in 1951, light-orange, mp

173\ ^{\circ}\mathrm{C}

, bp

249\ ^{\circ}\mathrm{C}

, stable to

450\ ^{\circ}\mathrm{C}

). A derivative of A was later prepared from 4-methoxyaniline with

\ce{NaQ}

. Oxidation with CAN at

-40\ ^{\circ}\mathrm{C}

in the presence of zinc nitrate gave the mixed salt

\ce{Zn(X)(NO3)}

(D). At

-20\ ^{\circ}\mathrm{C}

D decomposes releasing a gas and another salt

\ce{Zn(Q)(NO3)}

(E), containing the same elements as D, including 38.59 % zinc. The isomer F of B (obtained in 1999) is isoelectronic to iron compound G (a light-yellow liquid immiscible with cold water, used to prepare high-purity iron powder). In 2017 stable salt H was obtained: it contains

\ce{X-}

anions, chloride, ammonium and hydronium (

\ce{H3O+}

) cations, with 4.31 % H, 81.42 % N and 6.06 % Cl. (1) Write the molecular formulas of

\ce{HX}

, D, E, and identify A–C. (2) Write equations for the synthesis of

\ce{PhX}

by Huisgen and Ugi. (3) Identify F and G. (4) Calculate the formula of H.

Step 1 of 5: Zinc salt E and azide ion

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M(\ce{Zn(Q)NO3}) = \frac{65.38}{0.3859} = 169.42\ \text{g mol}^{-1} \Rightarrow M(\ce{Q}) = 169.42 - 65.38 - 62.00 = 42.04\ \text{g mol}^{-1} \Rightarrow \ce{Q} = \ce{N3-}

Analysis

The zinc fraction fixes the molar mass of E as 169.42 g mol $^{-1}$ ; subtracting $\ce{Zn^{2+}}$ (65.38) and $\ce{NO3-}$ (62.00) leaves 42.04 g mol $^{-1}$ , which matches $\ce{N3-}$ ( $3 \times 14.007 = 42.02$ ). Since D decomposed to E with gas evolution and contains the same elements, D is $\ce{Zn(N5)(NO3)}$ , the gas is $\ce{N2}$ , and $\ce{X-} = \ce{N5-}$ .