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  • Nuclear Magnetic Resonance Study of CO 2 Capture by Fluoroalkylamines: Ammonium Ion p K a Depression via Fluorine Modification and Thermochemistry of Carbamylation
Title: Nuclear Magnetic Resonance Study of CO 2 Capture by Fluoroalkylamines: Ammonium Ion p K a Depression via Fluorine Modification and Thermochemistry of Carbamylation
We are developing energy-efficient and reversible carbon capture and release (CCR) systems that mimic the Lys201 carbamylation reaction in the active site of ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCO). The multiequilibria scenario ammonium ion Xa ⇌ amine Xb ⇌ carbamic acid Xc ⇌ carbamate Xd requires the presence of both free amine and CO2 for carbamylation and is affected by the pKa(Xa). Two fluorination strategies aimed at ammonium ion pKa depression and low pH carbamylation were analyzed with (2,2,2-trifluoroethyl)butylamine 2b and 2,2-difluoropropylamine 3b and compared to butylamine 1b. The determination of K1 and ΔG1 of the carbamylation reactions requires the solution of multiequilibria systems of equations based on initial conditions, 1H NMR measurements of carbamylation yields over a wide pH range, and knowledge of K2– K5 values. K2 and K3 describe carbonic acid acidity, and ammonium ion acidities K4 were measured experimentally. We calibrated carbamic acid acidities K5 based on the measured value K6 of aminocarbamic acid using isodesmic reactions. The proton exchange reactions were evaluated with ab initio computations at the APFD/6-311+G* level in combination with continuum solvation models and explicit solvation. The utilities of 1–3 will be discussed as they pertain to the development of fluorine-modified RuBisCO-mimetic reversible CCR systems.  more » « less
Award ID(s):
2153206
PAR ID:
10510988
Author(s) / Creator(s):
; ;
Publisher / Repository:
ACS Publications
Date Published:
Journal Name:
The Journal of Organic Chemistry
Volume:
88
Issue:
16
ISSN:
0022-3263
Page Range / eLocation ID:
11534 to 11544
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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