# Tag Info

Accepted

### Why is −78 °C a magic temperature for organic reactions?

Dry ice (solid carbon dioxide) sublimes at −78 °C. Dry ice and acetone are a common cold bath for chemical reactions. The melting point of acetone is -95 °C so the bath never gets cold enough to ...
• 22.2k
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Thermodynamic and kinetic control This is a classic example of the concept of thermodynamic versus kinetic control of a reaction. Take a look at this energy profile diagram.1 The horizontal axis is a ...
• 70.8k
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### Python package for modelling chemical reactions

This is not really my area of expertise, but a quick search for "python chemical reactions" revealed three hits I've never seen before that may be of interest, the first one being closest to what you ...
• 7,378
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### How does heptafluoropropane suppress fire?

Curt F. is probably correct in his estimate that heptafluoropropane extinguishes fire primarily by physical means. According to an overview by Choy and Fong, 'An Introduction to Clean Agents: ...
• 6,981
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### Prove that a 10-Degree Temperature Increase Doubles the Rate Constant (k), when the Activation Energy is Approximately 50 kJ/mol

Your method and your mathematics seem perfectly fine, and your calculated result is correct. You are also quite correct that the result will change depending on the value of $E_\mathrm a$ that you ...
• 17.2k
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### Does high pressure reverse reaction between zinc and sulfuric acid?

As a very rough estimation of pressure when the hydrogen redox potential equals zinc standard redox potential, we can use the extrapolation of the Nernst equation: \begin{align} E^\circ_\ce{Zn/Zn^2+} &...
• 37.8k
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### Chemical oscillators that behave like a double pendulum

Before considering a double pendulum, let us consider a simple pendulum, which is modeled by $$\ddot \theta + \frac{g}{\ell} \sin (\theta) = 0$$ Choosing units that make $\frac{g}{\ell} =1$, we have ...
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### Why do we need sulfuric acid in creating alkyl bromide and not in creating alkyl iodide from alcohol and hydrogen halide?

I suspect $\ce{HBr}$ is produced in situ from $\ce{KBr}$ and $\ce{H2SO4}$. Same process isn't particularly suitable for $\ce{HI}$ generation as it reacts with $\ce{H2SO4}$: \ce{2HI + H2SO4 -> ...
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### Why should the temperature be maintained at 0–5 °C in a diazotisation?

The temperature at which many reactions are carried out is often arbitrary, with certain values being favoured due to the ease at which cooling baths can be prepared. As an example -78°C is highly ...
• 17.1k
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### Does gravity affect the rate of a chemical reaction?

It sort of depends what you mean. If by "affect the rate of a chemical reaction", you mean affect the individual steps of some overall reaction as to slow them down, then no, gravity definitely has no ...
• 12.9k
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### Formation of Aniline from Chlorobenzene

Your textbook's text is correct but the reaction image is incomplete. Reaction of chlorobenzene with ammonia in presence of both the cuprous chloride and cuprous oxide forms aniline but via two ...
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### Why does sulfonation of alcohols even work?

There are always two sides of a reaction. In the case of an alcohol attacking a sulphonic acid chloride, we can look closely at the alcohol and say: ‘Oh my, this is a bad nucleophile and we cannot ...
• 66.9k
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### Thermodynamic and kinetic products - carbocation stability

Background First off, let's discuss what we mean by "kinetic" and "thermodynamic" products. The kinetic product is the first formed product, the one that forms the fastest, the one with the largest ...
• 84k

### How does heptafluoropropane suppress fire?

That wikipedia page on gaseous fire suppression is not very good. It is very difficult for me to believe that pentafluoroethane has a different mechanism of fire suppression than heptafluoropropane. I ...
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### Why do we need sulfuric acid in creating alkyl bromide and not in creating alkyl iodide from alcohol and hydrogen halide?

The synthesis of alkyl halides from the corresponding aliphatic alcohols using concentrated hydrohalogen acids was investigated by Klein, Zhang and Jiang.[1] They note: [W]e found that the reflux ...
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### Does high pressure reverse reaction between zinc and sulfuric acid?

Any equilibrium calculation involving ordinary compounds that gives a pressure of $10^5$ bar or more is probably not realistic. Chemical bonds can deform and rearrange under such pressures and thus ...
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### Thermodynamic and kinetic products - carbocation stability

The product on the far left cannot form in any reasonable amounts. Consider the HOMO of s-cis-butadiene (which is a close enough model system to your dimethylcyclohexadiene): Those contributions that ...
• 66.9k

### A chamber to control concentration of a vapor: Is there a name for this equipment?

There is a book The Design of Controlled-atmosphere Chambers for the Study of Oxygen Toxicity, so I suggest "contolled-atmosphere chamber".
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### Formation of Acetal from Hemiacetal?

The acetal reaction is performed in $\ce{H+/ROH}$ condition (e.g., $\ce{H+/CH3OH}$). The general mechanism can be found in any Organic Chemistry textbook. The reaction is reversible. The first step is ...
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### How does the solvent determine whether mono- or tribromination of phenol occurs?

In aqueous medium, phenol is deprotonated to a certain extent, forming the phenoxide ion in which the ortho and para positions are even more activated than in phenol itself. Hence, trisubstitution ...
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### Does (chloromethoxy)ethane react in a bimolecular or monomolecular mechanism?

Probably both mechanisms can happen and it would require experimental data from reaction kinetics and computational calculations to determine which one of the mechanism is domintant. One example of ...

### Thermodynamic versus kinetic reactions

The terms are used in a different context to mean slightly different things. The kinetic product of a reaction is the one which is formed the fastest. In the case shown above this is the 1,2 product ...
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### Why do some reactions require specific pressures to happen?

ChemGuide has a good introductory article here. The effects of increasing pressure and temperature are, to an extent, equivalent. Increased pressure leads to increased collisions and increased ...
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### Dimethylene Cyclohexane to Octalin-1,4-Dione | Hydroboration vs. Ozonolysis Pros Cons

Comparison of the two approaches as far as yield/cost/etc. is void because one of them does not provide the same product as the other. Hydroboration-oxidation of 1,4-dimethylenecyclohexane yields 1,4-...
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### Noyori hydrogenation and the Curtin–Hammett principle

There's no way to predict this. Mnemonics are just rules, and rules are just rules. There will be exceptions, and you won't know when you should apply them a priori. If you could, it would be part of ...
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### Why do we need sulfuric acid in creating alkyl bromide and not in creating alkyl iodide from alcohol and hydrogen halide?

First of all, this question is very interesting. Though it looks simple at first glance, it really is complicated and we need to look at the details carefully. I am just going to shed some light on ...
• 24.9k
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### Why does phenolphthalein form in this reaction?

In the Org. Syn. link you provided phthalic anhydride 1 and p-chlorophenol 2 in 95% H2SO4 and boric acid at 200oC undergo condensation and cyclization. Phthalic anhydride 1 under acid catalysis reacts ...
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