How to determine which radicals are dominant in oxidation

In summary: Ultrasonic cavitation is a process whereby ultrasound incident upon a solution causes cavities and the change in pressure causes them to expand and collapse. The result is dissassociation and / or ionisation of the solution / soultion vapour that has entered the cavities via rectified diffusion. Radicals are produced. We determine the sonochemical "efficiency" or the production of OH radicals in KI solution by testing for triiodide (and infer this represents H2O2 production).Some say this is unreliable as other radicals can oxidise the I- ions.
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rwooduk
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I'm looking at the oxidation of I- ions by OH radicals to form iodine and finally triiodide.

This is a well known method of dosimetry, however some consider it flawed because during disassociation of solution other radicals are produced such as H or O radicals. They could also potentially oxidise the I- ions.

How would I show that the oxidation is caused primarily by the OH radicals?
 
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It sounds like you’re trying to describe iodometric titration, where you use an iodide solution to titrate a sample with an unknown amount of oxidant. The titration itself is not particularly sensitive to the type of oxidant. In fact, iodometric titration is usually used to measure H2O2 in solution. So I don’t think this is the best way to directly measure OH radicals. EPR might be a better bet.

Also, (brief aside) unless you’re inside the cooling water of a nuclear reactor, it’s exceedingly unlikely that free O or H atoms will be produced in solution. In fact, there’s a sizeable debate as to whether OH radicals are actually formed in solution. For example, in the Fenton reaction, which supposedly generates OH radicals transiently from hydrogen peroxide, there is some evidence that the oxidant is a hard-to-isolate oxo-iron open shell species.
 
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TeethWhitener said:
It sounds like you’re trying to describe iodometric titration, where you use an iodide solution to titrate a sample with an unknown amount of oxidant. The titration itself is not particularly sensitive to the type of oxidant. In fact, iodometric titration is usually used to measure H2O2 in solution. So I don’t think this is the best way to directly measure OH radicals. EPR might be a better bet.

Also, (brief aside) unless you’re inside the cooling water of a nuclear reactor, it’s exceedingly unlikely that free O or H atoms will be produced in solution. In fact, there’s a sizeable debate as to whether OH radicals are actually formed in solution. For example, in the Fenton reaction, which supposedly generates OH radicals transiently from hydrogen peroxide, there is some evidence that the oxidant is a hard-to-isolate oxo-iron open shell species.

Many thanks and apologies for the later reply. The process is ultrasonic cavitation whereby ultrasound incident upon a solution causes cavities and the change in pressure causes them to expand and collapse. The result is dissassociation and / or ionisation of the solution / soultion vapour that has entered the cavities via rectified diffusion. Radicals are produced. We determine the sonochemical "efficiency" or the production of OH radicals in KI solution by testing for triiodide (and infer this represents H2O2 production).

Some say this is unreliable as other radicals can oxidise the I- ions.

Thanks for your reply! From the sounds of it you agree that this is not an accurate method for determination of OH radicals.

Apologies for the delay in reply and I would welcome any more comments.
 

Related to How to determine which radicals are dominant in oxidation

1. How do you define dominant radicals in oxidation?

In oxidation, dominant radicals are those that have a higher reactivity and play a larger role in the overall reaction. They are typically the most stable radicals and are able to react with other molecules more readily.

2. What factors contribute to the dominance of a radical in oxidation?

The stability of a radical is the main factor that determines its dominance in oxidation. Factors such as bond strength, electron density, and resonance all contribute to the stability of a radical.

3. How can you experimentally determine the dominance of a radical in oxidation?

One way to determine the dominance of a radical in oxidation is by conducting a kinetic study, where the rate of reaction is measured for different radicals. The radical with the highest rate of reaction is likely the most dominant.

4. Can the dominance of a radical change in different reaction conditions?

Yes, the dominance of a radical can change in different reaction conditions. Factors such as temperature, pH, and the presence of other molecules can affect the stability and reactivity of a radical, thus changing its dominance in oxidation.

5. Are there any computational methods to determine the dominance of a radical in oxidation?

Yes, there are computational methods such as quantum mechanics calculations and molecular modeling that can be used to predict the dominance of a radical in oxidation. These methods take into account the molecular structure and properties of the radical to determine its stability and reactivity.

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