CHETAH 9.0CHETAH 9.0

ASTM E27-07ASTM E27-07

TutorialTutorial

CHETAHCHETAH®® Computer Program for Energy Release Evaluation and Computer Program for Energy Release Evaluation and Prediction of Chemical Thermodynamic PropertiesPrediction of Chemical Thermodynamic Properties..

The CHETAHThe CHETAH®® program is a unique tool for predicting program is a unique tool for predicting both thermochemical and flammability properties and both thermochemical and flammability properties and certain reactive chemicals hazards associated with a pure certain reactive chemicals hazards associated with a pure chemical, a mixture of chemicals, or a chemical reaction. chemical, a mixture of chemicals, or a chemical reaction. The calculations are made using only information The calculations are made using only information concerning the molecular structure of the components.concerning the molecular structure of the components.

Capabilities of CHETAHCapabilities of CHETAH

ThermochemistryThermochemistry heats of reactionheats of reaction heat of combustionheat of combustion equilibrium constantsequilibrium constants misc. thermodynamic propertiesmisc. thermodynamic properties

““Energy Release Evaluation”Energy Release Evaluation” tendency for a material to “explode”tendency for a material to “explode”

Predicts Lower Flammable Limit and other flammability Predicts Lower Flammable Limit and other flammability propertiesproperties

Unique CapabilitiesUnique Capabilities

Largest Database for Benson Groups Largest Database for Benson Groups (886!)(886!) Suggests substitutes for missing groups! Suggests substitutes for missing groups!

Prediction of Reactive Chem. Hazards (ERE)Prediction of Reactive Chem. Hazards (ERE)

Large whole molecule database: from DIPPR Large whole molecule database: from DIPPR (1200 (1200 species!)species!)

Database for Liquid and Solid Benson GroupsDatabase for Liquid and Solid Benson Groups

Database for Species in Aqueous SolutionDatabase for Species in Aqueous Solution

Benson’s Method ExampleBenson’s Method Example

Atom Atom Benson Benson Contribution to Contribution to Group Group ∆H∆Hff(g), kcal/mol(g), kcal/mol

11 NH2 - ( C)NH2 - ( C) 4.80 4.8022 CH2 - ( N, C)CH2 - ( N, C) -6.60-6.6033 CH2 - (2C)CH2 - (2C) -4.93-4.9344 CHCl - (2C)CHCl - (2C) -14.80-14.8055 CH - (O, 2C)CH - (O, 2C) -7.20-7.20

66 OH - (C)OH - (C) -37.88-37.8877 CH3 - ( C)CH3 - ( C) --10.0810.08

Total: -76.69Total: -76.69

Cl

OH

H2N

12

3 4

5

6

7

Don’t Know How to Specify Benson Groups? Don’t Know How to Specify Benson Groups? Don’t Despair!Don’t Despair!Graphical User Interface May Be Used:Graphical User Interface May Be Used:•Uses ChemDraw®

Molecular Drawing

Software

•Save structure

as “SMILES” string

•Cut and Paste

into CHETAH

•Automatically converts to Benson groups!

ASTM CHETAHASTM CHETAHThermodynamic Table DemoThermodynamic Table Demo

Main Screen for CHETAH. The user can directly enter the molecules from the database or use Benson groups to describe the new molecule.

As an alternative, we can describe the molecule using an appropriate molecular drawing program. Here we draw a molecule in ChemdrawTM Software ( www.camsoft.com)

Next we select the drawn molecule and copy it as a SMILES string

We now return to the CHETAH program and choose SMILES Input. Next we paste the SMILES string we copied from the other application and choose OK.

Now we see a screen showing the Benson groups composing the molecules. We select Next.

Select “Thermodynamic Table” from the “Calculations” menu.

Next we see a screen asking for information relating to the Thermodynamic Table that we wish to calculate. Select “Calculate”.

The following is the resulting table of calculated thermodynamic values

Liquid Benson GroupsLiquid Benson Groups

A database is provided of Benson Groups that may be used to A database is provided of Benson Groups that may be used to describe molecules that are in the liquid phase. Molecules describe molecules that are in the liquid phase. Molecules constructed from these Benson Groups may then be used in certain constructed from these Benson Groups may then be used in certain calculations within CHETAH. calculations within CHETAH.

Thermodynamic properties of the molecule in the liquid phase may Thermodynamic properties of the molecule in the liquid phase may be calculated using the Thermodynamic Table option. Also these be calculated using the Thermodynamic Table option. Also these liquid molecules may be constituents in a chemical reaction liquid molecules may be constituents in a chemical reaction calculation that may involve gas, liquid, solid, and aqueous species.calculation that may involve gas, liquid, solid, and aqueous species.

Note that Benson Groups for liquids are mainly useful for Note that Benson Groups for liquids are mainly useful for describing pure liquid organic molecules. Elsewhere in CHETAH describing pure liquid organic molecules. Elsewhere in CHETAH is found a database of species in aqueous solution which may also is found a database of species in aqueous solution which may also be useful.be useful.

In describing a molecule it is not appropriate to mix liquid groups In describing a molecule it is not appropriate to mix liquid groups with gas or solid Benson groups. The liquid molecule should only with gas or solid Benson groups. The liquid molecule should only be composed of liquid Benson Groups.be composed of liquid Benson Groups.

The database of liquid Benson groups consists of 397 groups. Note The database of liquid Benson groups consists of 397 groups. Note that molecules that are built from these groups often require that molecules that are built from these groups often require corrections to be added as additional groups for highest accuracy. corrections to be added as additional groups for highest accuracy.

The liquid Benson groups and their corrections are an The liquid Benson groups and their corrections are an implementation of the publication by E.S. Domalski and E.D. implementation of the publication by E.S. Domalski and E.D. Hearing, J. Phys. Chem. Ref. Data, 22(4), 816-829, 1993.Hearing, J. Phys. Chem. Ref. Data, 22(4), 816-829, 1993.

Example: “Ethanol”Example: “Ethanol”

Ethanol, C2H5OH will be used as an example for the entry of a Ethanol, C2H5OH will be used as an example for the entry of a pure liquid compound using Benson Groups. Pure compound pure liquid compound using Benson Groups. Pure compound properties will be calculated in this example for ethanol.properties will be calculated in this example for ethanol.

The user can use Liquid Benson groups to describe the molecule The user can use Liquid Benson groups to describe the molecule on the main screen. on the main screen.

We select next . ThenWe select next . Then select “Thermodynamic Table” from the select “Thermodynamic Table” from the “Calculations” menu.“Calculations” menu.

Next we see a screen asking for information relating to the Next we see a screen asking for information relating to the Thermodynamic Table that we wish to calculate. Select Thermodynamic Table that we wish to calculate. Select “Calculate”.“Calculate”.

The following is the resulting table of calculated The following is the resulting table of calculated thermodynamic valuesthermodynamic values

Molecule made of solid Benson groups:Molecule made of solid Benson groups:

A database is provided of Benson Groups that may be used A database is provided of Benson Groups that may be used to describe molecules that are in the solid phase. to describe molecules that are in the solid phase.

Molecules constructed from these Benson Groups may then Molecules constructed from these Benson Groups may then be used in certain calculations within CHETAH. be used in certain calculations within CHETAH.

Thermodynamic properties of the molecule in the solid phase Thermodynamic properties of the molecule in the solid phase may be calculated using the Thermodynamic Table option. may be calculated using the Thermodynamic Table option. Also these solid molecules may be constituents in a chemical Also these solid molecules may be constituents in a chemical reaction calculation that may involve gas, liquid, solid, and reaction calculation that may involve gas, liquid, solid, and aqueous species.aqueous species.

Note that Benson Groups for solids are mainly useful for Note that Benson Groups for solids are mainly useful for describing solid organic molecules. Elsewhere in CHETAH describing solid organic molecules. Elsewhere in CHETAH is found a database of ionic crystal type molecules which are is found a database of ionic crystal type molecules which are typically inorganic. typically inorganic.

Also CHETAH provides a predictive method for properties of Also CHETAH provides a predictive method for properties of inorganic crystals based on a combination of ion based groups.inorganic crystals based on a combination of ion based groups.

In describing a molecule it is not appropriate to mix solid In describing a molecule it is not appropriate to mix solid groups with gas or liquid Benson groups. The solid molecule groups with gas or liquid Benson groups. The solid molecule should only be composed of solid Benson Groups.should only be composed of solid Benson Groups.

The database of solid Benson groups consists of 306 groups. The database of solid Benson groups consists of 306 groups. Note that molecules that are built from these groups often Note that molecules that are built from these groups often require corrections to be added as additional groups for highest require corrections to be added as additional groups for highest accuracy. accuracy.

The solid Benson groups and their corrections are an The solid Benson groups and their corrections are an implementation of the publication by E.S. Domalski and E.D. implementation of the publication by E.S. Domalski and E.D. Hearing, J. Phys. Chem. Ref. Data, 22(4), 816-829, 1993.Hearing, J. Phys. Chem. Ref. Data, 22(4), 816-829, 1993.

Example: “Acryl amide”Example: “Acryl amide” Acryl amide will be used for an example of direct entry and Acryl amide will be used for an example of direct entry and

calculation of properties for a solid compound composed of Solid calculation of properties for a solid compound composed of Solid Benson Groups. Benson Groups.

The user can use Solid Benson Groups to describe the molecule on The user can use Solid Benson Groups to describe the molecule on the main screen.the main screen.

Select “Thermodynamic Table” from the “Calculations” menu.Select “Thermodynamic Table” from the “Calculations” menu.

Next we see a screen asking for information relating to the Next we see a screen asking for information relating to the Thermodynamic Table that we wish to calculate. Select Thermodynamic Table that we wish to calculate. Select

“Calculate“Calculate

The following is the resulting table of calculated The following is the resulting table of calculated thermodynamic valuesthermodynamic values

Aqueous Species:Aqueous Species:

A database is provided of chemical species in aqueous solution. The A database is provided of chemical species in aqueous solution. The chemical formula is given followed by an indication of the chemical formula is given followed by an indication of the concentration in water.concentration in water.

There are 875 aqueous species records in this database.There are 875 aqueous species records in this database.

Thermodynamic properties of the species in aqueous solution may Thermodynamic properties of the species in aqueous solution may be calculated using the Thermodynamic Table option. be calculated using the Thermodynamic Table option.

Also the species in aqueous solution may be constituents in a Also the species in aqueous solution may be constituents in a chemical reaction calculation that may involve gas, liquid, and solid chemical reaction calculation that may involve gas, liquid, and solid pure species and species in aqueous solution.pure species and species in aqueous solution.

Most species in this database give the name of chemical compound Most species in this database give the name of chemical compound followed by the amount of water the species is dissolved in. followed by the amount of water the species is dissolved in. However some species are represented by the chemical name and However some species are represented by the chemical name and special nomenclature indicating the amount of water as follows:special nomenclature indicating the amount of water as follows:

aq aq aqueous solution, concentration not specifiedaqueous solution, concentration not specified ai ai aqueous solution, ionized substance standard, m = 1 mol/kgaqueous solution, ionized substance standard, m = 1 mol/kg ao ao aqueous solution, un-ionized substance, standard state,aqueous solution, un-ionized substance, standard state, m = 1 mol/kg, or an ion for which here no further ionization is m = 1 mol/kg, or an ion for which here no further ionization is

consideredconsidered

The database of Aqueous Species consists of 875 records. The The database of Aqueous Species consists of 875 records. The source of the data is: D.D. Wagman, W.H. Evans, V.B. Parker, source of the data is: D.D. Wagman, W.H. Evans, V.B. Parker, R.H. Schumm, I. Halow, S.M. Bailey, K.L. Churney, and R. L. R.H. Schumm, I. Halow, S.M. Bailey, K.L. Churney, and R. L. Nuttall, The NBS Tables of Chemical and Thermodynamic Nuttall, The NBS Tables of Chemical and Thermodynamic Properties, Journal o f Physical Chemical Reference Data, Vol. 11, Properties, Journal o f Physical Chemical Reference Data, Vol. 11, 1982, Supplement No. 2.1982, Supplement No. 2.

Example: “HCl in 1000 H2O”Example: “HCl in 1000 H2O” Enter the molecules using aqueous Benson groups to describe Enter the molecules using aqueous Benson groups to describe

the new molecule on the main screen.the new molecule on the main screen.

We select next . Then select “Thermodynamic Table” from the We select next . Then select “Thermodynamic Table” from the

“Calculations” menu“Calculations” menu

Next we see a screen asking for information relating to the Next we see a screen asking for information relating to the Thermodynamic Table that we wish to calculate. Select “CalculateThermodynamic Table that we wish to calculate. Select “Calculate”.”.

The following is the resulting table of calculated thermodynamic The following is the resulting table of calculated thermodynamic valuesvalues

ASTM CHETAHASTM CHETAHCombustion Calculations DemoCombustion Calculations Demo

CHETAH Heat of CombustionCHETAH Heat of Combustion

CHETAH can calculate heat of combustion for any CHETAH can calculate heat of combustion for any compound or mixture composed of any of approximately compound or mixture composed of any of approximately 70 elements in the Periodic Table.70 elements in the Periodic Table.

CHETAH calculates the heat of combustion based on the CHETAH calculates the heat of combustion based on the reactant(s) being ideal gases at 298 K.reactant(s) being ideal gases at 298 K.

CHETAH chooses combustion products based on a CHETAH chooses combustion products based on a standard set of rules.standard set of rules.

On this screen the user can enter whole molecules from the database or from Benson groups. Here we search for the chemical Phenol.

The search box was used to locate phenol in the gas molecules database. The component phenol is then selected and “Add Group” is clicked.

Note the changes. Phenol has been added in first row of the first column with its molecular weight shown above.

Select the name bar above the first column and enter the desired name for the component.

Choose “Combustion Heat” from “Calculations” menu.

Next we see a screen asking for information related to Combustion Calculations. Select “Calculate”.

These are the results for the combustion calculations.

ASTM CHETAHASTM CHETAH

Energy Release Calculations DemoEnergy Release Calculations Demo

CHETAH for Reactive Hazard CHETAH for Reactive Hazard EvaluationEvaluation

 •Conservative screening tool .

•Energy related hazards frequently not known .

•Experimentally determined thermochemical data are often not available .

•CHETAH can perform an energy release evaluation based on structure only.

•Can give the maximum energy of decomposition .

•Hazard evaluations are valid for gas, liquid, or solid materials.

On this screen the user can enter molecules from the database or from Benson groups. Here we will enter Tri Nitro Toluene (TNT) from Benson groups.

For TNT, select Benson Groups as shown on the following slides.Enter the numbers of each group in the ‘Count’ column.

This completes the selection of groups for TNT.

Select “Energy Release” from the “Calculations” menu.

Next we see a screen asking for information related to Energy Release Evaluation. Select “Calculate”.

This screen represents the results of the calculations.

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Maximum Heat of DecompositionMaximum Heat of Decomposition

•Easiest to understand and most intuitively sound

•In a material capable of harmful energy release, all of the energy is obtained from the material itself

•CHETAH chooses products which maximize the enthalpy of decomposition

ASTM CHETAHASTM CHETAHChemical Reaction Evaluation Chemical Reaction Evaluation

Reaction Thermo chemistry in CHETAHReaction Thermo chemistry in CHETAH

• Build all species

• Click on Reaction button

• Specify stoichiometry

Cl

+ H2O

Cl

OH

CH3 - (C)CHCl - (C, =C)=CH - (C)=CH2

CH3-(C) CHCl-(2C) CH2-(2C)

CH2-(C,O)OH-(C)

Think Simplification!!!Think Simplification!!! "Analog Reaction Hypothesis" states that the heats of reaction

for structurally similar reactions are identical

Example: R(g) + Cl2(g) => R-Cl(g) + HCl(g)

– Species, R ∆ rH, kcal/mol, 25 C– Ethane -28.8– Octane -29.3– Toluene -29.6– Naphthalene -29.4

Example of a Reaction Which can be Simplified:Example of a Reaction Which can be Simplified:

+CH CH2 NH2 CH Cl CH2 CH C CH C O

OH

CH CH2 NH CH CH2 CH C CH CO

OHHCl+

Simplified Analog Reaction:Simplified Analog Reaction:

NH2 + Cl

N+ HCl

On this screen the user can enter molecules from the database or from Benson groups. Here we will describe the reaction between sulfuric acid and sodium hydroxide.

Select all the components for both reactants and products.

Select “Chemical Reaction” from “Calculations” menu.

Change the classification according to Reactant or Product. Balance the reaction by choosing the number of moles. Select “Calculate”.

Results are now shown.Page 1 of 2

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Example: “Reaction between HCl and NaOH”.Example: “Reaction between HCl and NaOH”.

HCl (in 1000ml H2O)+NaOH (in 1000 ml H2O) =>HCl (in 1000ml H2O)+NaOH (in 1000 ml H2O) => NaCl(in 2000ml H2O)+ H2O(liq)NaCl(in 2000ml H2O)+ H2O(liq)

On this screen the user can enter molecules from the On this screen the user can enter molecules from the database or from Benson groups.database or from Benson groups.

Here we will describe a reaction between hydrochloric acid Here we will describe a reaction between hydrochloric acid and sodium hydroxide.and sodium hydroxide.

Select all the components for both reactants and productsSelect all the components for both reactants and products

Select “Chemical Reaction” from “Calculations” menu.Select “Chemical Reaction” from “Calculations” menu.

Change the classification according to Reactant or Product. Change the classification according to Reactant or Product. Balance the reaction by choosing the number of moles.Balance the reaction by choosing the number of moles. Select “Calculate”.Select “Calculate”.

The following results appear on screenThe following results appear on screen..

Example : Formation of acetic acidExample : Formation of acetic acid

On this screen the user can enter molecules from the On this screen the user can enter molecules from the database or from Benson groups.database or from Benson groups.

Here we describe the reaction which involves formation of Here we describe the reaction which involves formation of acetic acid.acetic acid.

2H2O (g) + 2C (ref state) => CH3COOH (liq)2H2O (g) + 2C (ref state) => CH3COOH (liq) (Or)(Or) CH3 – (CO) liqCH3 – (CO) liq CO – (C, O) liqCO – (C, O) liq OH – (CO) liqOH – (CO) liq

Select all the components for both reactants and products.Select all the components for both reactants and products.

Select “Chemical Reaction” from “Calculations” menu.Select “Chemical Reaction” from “Calculations” menu.

Change the classification according to Reactant or Product. Change the classification according to Reactant or Product.

Balance the reaction by choosing the number of moles.Balance the reaction by choosing the number of moles.

Select “CalculateSelect “Calculate

The following results appear on screenThe following results appear on screen..

Phase EffectsPhase Effects

•CHETAH Calculations are often gas phase values! The largest database is a gas phase database.

•If chemistry takes place in condensed phase (i.e. in a solvent), corrections need to be considered, if your calculations are in the gas phase.

•many times these corrections cancel but not always!

•Rule of thumb: vaporiz. heat = 100cal/g (150 cal/g for a H-bonded species, 80 cal/g for a chlorinated species)

•Estimation methods for heat of vaporization are available.

ASTM CHETAHASTM CHETAH

Flammability Flammability

CHETAH FlammabilityCHETAH Flammability

CHETAH calculates LFL, LOC, MIE and a number of CHETAH calculates LFL, LOC, MIE and a number of other flammability parameters using Britton’s method.other flammability parameters using Britton’s method.

CHETAH will calculate LFL at temperatures besides 298 K.CHETAH will calculate LFL at temperatures besides 298 K.

CHETAH also calculates LFL by Bothwell’s method.CHETAH also calculates LFL by Bothwell’s method.

CHETAH can calculate LFL for mixturesCHETAH can calculate LFL for mixtures..

To find the flammability parameters of a gas mixture, the user should enter molecules from the Gas Molecules database or enter molecules by the use of ideal Benson Groups.

Here Propane and N-butane have been selected fromthe Gas Molecules database.

After selecting the components, choose “Flammability” from the “Calculations” menu.

Next we see a screen asking for the composition of the mixture.Choose the amount of each chemical. Select “Calculate”.

The first part of the results page for this flammability example. This part shows results from Britton’s method.

This section highlights predictions by Bothwell’s method.

Clicking on “Definitions” will display a list of Clicking on “Definitions” will display a list of definitionsdefinitions

•LFL: The Lower Flammable Limit is the minimum concentration of a combustible substance that is capable of propagating a flame through a homogeneous mixture of the combustible and a gaseous oxidizer under specified conditions. •LOC: The Limiting Oxygen Concentration of a fuel-oxidant-inert system is the oxygen (oxidant) concentration at the limit of flammability for the worst case (most flammable) fuel concentration.

•Etc. for LLFT, T-max, Su, qd, MIE

The End The End