The kinetics of the isotope exchange reactions of RCH(COOH) 2 (R"H, D, Me, Et, Bu, and Ph) in D 2 O solution were studied by using 1 H NMR spectroscopy. It was observed that the rate of isotope exchange reaction was inhibited by the presence of 1 M of DNO 3 , DCl, DBr or D 2 SO 4 and catalyzed by the presence of 4 M of D 2 SO 4 . No inhibition effect was observed in the case of D 3 PO 4 . The effect of inorganic acids follows the order of D 3 PO 4 Ͼ D 2 SO 4 Ͼ Ͼ (DNO 3 , DCl, DBr). The conjugated base (RCH(COOD)(COO Ϫ )) of RCH(COOD) 2 plays an important role in the isotope exchange reaction. The presence of deuterium ion suppresses the generation of RCH(COOD)(COO Ϫ ) ion from RCH(COOD) 2 and inhibits the rate of isotope exchange. In general, the order of reactivity of RCH(COOH) 2 toward isotope exchange with deuterium atom is R" Ph Ͼ (H, Br) Ͼ Me Ͼ (Et, Bu).
The substitution reaction of benzal chloride (PhCHCl2) and sodium iodide in acetone needs a metal‐ion catalyst. Without considering the effects of solubility and the dissociation of salt, salts of Cr(III), Mn(II), Fe(II, III), Co(II), Ni(II), Cu(II)m Zn(II), Cd(II), Hg(I, II), and Sb(III) ions are used to study their catalytic reactivities. It is found that the Fe(II) ion exhibits acceptable catalytic effect. The overall Fe(II)‐catalyzed PhCHCl2‐NaI reaction can be described by the following competitive consecutive scheme: PhCHCl2 → PhCHCII → PhCHI2. Under suitable conditions, coupling products such as PhCH=CHPh and PhCHClCHClPh are also found. The rate of the first‐stage substitution of the PhCHCl2‐NaI reaction increases linearly with the PhCHCl2 concentration. It increases asymptotically with the FeCl2 concentration. However, there is an optimum concentration for Nal. The apparent activation energies are 104 ± 4 kJ/mol and 133 ± 4 kJ/mol for the Fe(II)‐catalyzed PhCHCl2‐NaI and PhCHCH‐NaI reactions, respectively.
The isotope exchange reactions of malonic acid and a malonate ion were investigated in acidic and basic D2O solutions, respectively, using 1H NMR spectroscopy. The isotope exchange reaction of malonic acid is inhibited by the presence of DNO3 (0–3 M) and DSO4− ion (0–0.1 M), whereas it is catalyzed by the presence of DSO4− ion (> 0.2 M), D3PO4, D2PO4− ion or DPO42– ion. The order of relative reactivity for catalyzing the isotope reaction of malonic acid in D2O is DPO42– > D2PO4− > D3PO4 > DSO4− > DNO3. The rate of the isotope exchange reaction of malonate ion in D2O decreases to a minimum and then increases with increased [NaOD]0. The mechanism of the isotope exchange reaction of malonic acid in acidic D2O is different from the general acid‐catalyzed mechanism generally observed for organic acids like acetic and dichloroacetic acids. The bimalonate ion plays an important role in the isotope exchange reactions of this system.
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