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The hydrolysis of geminal ethers: a kinetic appraisal of orthoesters and ketals

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ABSTRACT

A novel approach to protecting jet fuel against the effects of water contamination is predicated upon the coupling of the rapid hydrolysis reactions of lipophilic cyclic geminal ethers, with the concomitant production of a hydrophilic acyclic hydroxyester with de-icing properties (Fuel Dehydrating Icing Inhibitors - FDII). To this end, a kinetic appraisal of the hydrolysis reactions of representative geminal ethers was undertaken using a convenient surrogate for the fuel–water interface (D2O/CD3CN 1:4). We present here a library of acyclic and five/six-membered cyclic geminal ethers arranged according to their hydroxonium catalytic coefficients for hydrolysis, providing for the first time a framework for the development of FDII. A combination of 1H NMR, labelling and computational studies was used to assess the effects that may govern the observed relative rates of hydrolyses.

No MeSH data available.


Hydroxonium catalytic coefficients (kH+ M−1 s−1 including standard errors where appropriate) for 1–16 as determined in this study. a,bValues of kH+ determined via calibration with respect to 8 [18] and 16 [23], respectively (see Experimental section).
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Figure 1: Hydroxonium catalytic coefficients (kH+ M−1 s−1 including standard errors where appropriate) for 1–16 as determined in this study. a,bValues of kH+ determined via calibration with respect to 8 [18] and 16 [23], respectively (see Experimental section).

Mentions: For acyclic geminal ethers stage 1 is invariably rate limiting, i.e., k3 > k1. For cyclic systems k−3 becomes more dominant in the pH range of about 4–6 [23], however stage 1 remains rate limiting [26]. The overall rate of reaction can therefore be established by measuring the consumption of the geminal ether [27]. We present here kinetic data measured for a range of acyclic orthoformates, orthoacetates, 1,3-dioxolane orthoesters, oxanes, and 1,3-dioxanes (Fig. 1), and consider the factors which may modulate the rates of hydrolyses.


The hydrolysis of geminal ethers: a kinetic appraisal of orthoesters and ketals
Hydroxonium catalytic coefficients (kH+ M−1 s−1 including standard errors where appropriate) for 1–16 as determined in this study. a,bValues of kH+ determined via calibration with respect to 8 [18] and 16 [23], respectively (see Experimental section).
© Copyright Policy - Beilstein
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4979634&req=5

Figure 1: Hydroxonium catalytic coefficients (kH+ M−1 s−1 including standard errors where appropriate) for 1–16 as determined in this study. a,bValues of kH+ determined via calibration with respect to 8 [18] and 16 [23], respectively (see Experimental section).
Mentions: For acyclic geminal ethers stage 1 is invariably rate limiting, i.e., k3 > k1. For cyclic systems k−3 becomes more dominant in the pH range of about 4–6 [23], however stage 1 remains rate limiting [26]. The overall rate of reaction can therefore be established by measuring the consumption of the geminal ether [27]. We present here kinetic data measured for a range of acyclic orthoformates, orthoacetates, 1,3-dioxolane orthoesters, oxanes, and 1,3-dioxanes (Fig. 1), and consider the factors which may modulate the rates of hydrolyses.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

A novel approach to protecting jet fuel against the effects of water contamination is predicated upon the coupling of the rapid hydrolysis reactions of lipophilic cyclic geminal ethers, with the concomitant production of a hydrophilic acyclic hydroxyester with de-icing properties (Fuel Dehydrating Icing Inhibitors - FDII). To this end, a kinetic appraisal of the hydrolysis reactions of representative geminal ethers was undertaken using a convenient surrogate for the fuel–water interface (D2O/CD3CN 1:4). We present here a library of acyclic and five/six-membered cyclic geminal ethers arranged according to their hydroxonium catalytic coefficients for hydrolysis, providing for the first time a framework for the development of FDII. A combination of 1H NMR, labelling and computational studies was used to assess the effects that may govern the observed relative rates of hydrolyses.

No MeSH data available.