First principles computational study on hydrolysis of water-reactive chemicals phosphorus trichloride and oxychloride

(PCl3 and POCl3)

Hyunwook Jung, Joonhee Kang, Hoje Chun, Byungchan Han

Department of Chemical and Biomolecular Engineering, Yonsei University, 03722, Seoul, Republic of Korea

15th June 2018

Motivation

PCl3(Phosphorus Trichloride)

POCl3(Phosphorus Oxychloride)

04 2₩

03 2₩

• Chemical Properties

- Colorless Liquid

- Density: 1.576g g/cm3

- Vapour pressure: 100mmHg

• Common Uses

• Chemical Properties

- Colorless Liquid

- Density: 1.576g g/cm3

- Vapour pressure: 100mmHg

• Common Uses

Y. Segall et al. Chem. Res. Toxicol. 2003, 16, 350-356

World production of PCl3 & POCl3 exceeds more than 1/3 million tons annually

They are essential chemicals in industry because of their versatile uses

Pesticides Flame Retardant

Chelating Agent Plastic Additives

N-type Dopant Solar Cell

IC Optical Fiber

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Motivation

Tianjin Explosion (China)Deaths: 173 Cause: NaCN, NH4NO3, …

12 Aug. 2015

2 Dec. 1984

Bhopal Disaster (India)Death: at least 3787Cause: Methyl isocyanate

Gumi HF leakage (Korea)Deaths: 5Cause: HF

27 Sep. 2012

21 Sep. 2001

AZF Disaster (France)Death: 30Cause: NH4NO3

Chemical disasters from unexpected reaction

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Yet, reaction database is far from completeness, which hinders safe control of

chemical accident

Motivation

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Physicochemical, Toxicological,

EcotoxicologicalProperties

Experiments, Animal testing

Computer Simulation, Ab-initio calculation

Conventional approach

Alternative approach

REACH Regulations in EU(Registration, Evaluation, Authorization, and Restriction of Chemicals)

Carlos Nieto-Draghi et al. 2015. Chem. Rev. 115 (24) 13093-13164

Experiment Ab-initio CalculationReliable but,

Not realistic in time, cost, feasibility, and safety

Fast, low cost, and very safe.

Measurement methods of required physicochemical properties

Outline

1. Motivation

2. Model Systems and Computational Details

3. Results and Discussion- Water-catalyzed hydrolysis

- Structural analysis

- Solvent effect by water and charge analysis

- Potential energy surface profile

4. Summary

5. Acknowledgement5

Model Systems

Calculated using:

Gaussian09

B3LYP 6-31+g(d,p)

Model Systems and Computational Details

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Grotthuss Mechanism; three-fold role of water

water

Reactant

Solvent

Catalyst

H2O

PCl3

Water-Catalyzed HydrolysisFree energy diagram

PCl3(g) + 3H2O(g) → H3PO3(g) + 3HCl(g) POCl3(g) + 3H2O(g) → H3PO4(g) + 3HCl(g)

PCl3 POCl31st step -5.88 -8.852nd step -0.19 -9.843rd step -3.98 -8.34

Tautomerization -3.67 -ΔH -13.73 (-15.44) -27.03 (-24.1)

Table 1. Reaction heat for each steps of the hydrolysis and experimental data (in parenthesis)

7H. Jung et al. Journal of Hazardous Materials 341 (2018) 457-463

Structural AnalysisTorsional angle as key-descriptor of kinetics

StepTorsional

AnglePCl3 Torsional

AnglePOCl3

High ∆ ‡ Low ∆ ‡ High ∆ ‡ Low ∆ ‡

1st Cl1Cl2PCl3 150.26˚ 91.63˚ Cl1Cl2PO 157.87˚ 177.57˚

2nd Cl1Cl2PO 148.70˚ 91.16˚ O1ClPO2 151.06˚ 167.66˚

3rd ClO1PO2 146.33˚ 79.07˚ ClO1PO2 150.96˚ 151.89˚

Table 2. Torsional angle around central Phosphorus in the transition states

See-saw

Trigonal bipyramidal

C C PCl 90°

C C 180°

8H. Jung et al. Journal of Hazardous Materials 341 (2018) 457-463

° °

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Slide 8

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Solvent Effect by Water: Charge Analysis

Charge Density Distribution

Hybridization shift(sp3→sp3d) is qualitatively confirmed 9

H. Jung et al. Journal of Hazardous Materials 341 (2018) 457-463

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‡

PCl3+n·H2OPCl2(OH)+HCl

POCl3+n·H2O

‡‡

POCl2(OH)+HCl

Typical gas phase SN2 reaction has double-well PES profile (PCl3)

POCl3 has triple-well PES profile; Due to additional coordination by

double bonded Oxygen

Potential Energy Surface Profile

H. Jung et al. Journal of Hazardous Materials 341 (2018) 457-463

Summary

Adjacent water molecules play key role as a catalyst toward hydrolysis

reaction via proton transfer.

Torsional angle around phosphorus atom is key-descriptor of the kinetics.

Hybridization of phosphorus is shifted from sp3 to sp3d at transition state.

Activated complex with charge separation was more stabilized by water.

PCl3 and POCl3 have different potential energy profile due to different

coordination around phosphorus.

11H. Jung et al. Journal of Hazardous Materials 341 (2018) 457-463

Acknowledgement

This work was supported by

• The Korea Ministry of Environment (MOE) as “the Chemical Accident

Prevention Technology Development Project”

• Global Frontier Program through the Global Frontier Hybrid Interface

Materials (GFHIM) (2013- M3A6B1078882)

• The Defense Industry Technology Center (DITC) for financial support from

contract No.UC15000ID

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Thank you for your attention!!

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Contact Info. Hyunwook Jung

Email: jungsdao@gmail.comPhone: +82-10-2780-2396