Episode #125 of the Stack Overflow podcast is here. We talk Tilde Club and mechanical keyboards. Listen now
50

Probably the biggest drivers behind using methane as a fuel is that it is abundant in natural gas and is (currently) mostly useless as a chemical feedstock. Ethane makes up a few percent of natural gas and can also be obtained as byproducts of petroleum refining, but the big difference from methane is that ethane is extremely useful in chemical synthesis (...


37

In both cases, there appears to be a confusion of terminology between common and technical uses. We commonly use methane and propane for cooking (and home heating), but not ethane. I would expect ethane to be suitable for this, being in between the two, but I've never heard of anyone using it for this purpose. Why is that? In reality, anyone using ...


35

These polyspiro compounds such as the one you gave are known as [m,n]rotanes, where m is the size of the central ring and n is the size of the decorating rings. So, your compound would be called [5,5]-rotane. A Reaxys search unfortunately doesn't show anything for [5,5]-rotane, but in general, many such compounds have been made. A lot of the articles are in ...


27

To clarify @ron's point, the general "cheminformatics" rule for deducing aromatic fused-ring systems is whether there is one path (usually the peripheral one) that satisfies $4n+2$: So for naphthalene: The bold bonds give you a ring path of $\mathrm{sp^2}$ carbons with 10 π electrons, so it's aromatic. There are some arguments about whether the central ...


25

Pyrene is aromatic. The Hückel $4n+2$ rule works best with monocyclic ring systems. If you look at the following resonance structure for pyrene with a central double bond, the monocyclic periphery has 14 π electrons (ignoring the greyed-out central double bond), but that is a rationalization. Nonetheless, pyrene undergoes reactions characteristic of ...


22

Yes, based on what we can see in the video, your guess appears to be correct: as the propane-filled bottle warmed up, just enough propane evaporated to keep the pressure inside the bottle equal to the equilibrium vapor pressure of the liquid propane. According to the video, the ambient temperature outside at the time it was recorded was "about 45 °...


20

This is a very good question and if popular books give conflicting answers, then it must be reasoned out. Unfortunately, Paula Bruice has given the wrong answer while the other two books have given no explanation for this comparison. For the answer I assume that you know about hyperconjugation and the various contributing structures it involves. This gives ...


19

Very interesting question, and it kept me up despite daylight saving time cheating me of one hour of sleep last night... A good reference is Albright, Burdett and Whangbo, Orbital Interactions in Chemistry 2nd ed. pp 282ff. which explains this in much greater detail than I can. (In general, that book is fantastic.) I will try my best to summarise what they ...


18

Your intuition is indeed correct! Several sources provide the same answer (1, 2, 3). Perhaps the simplest and most direct evidence comes from comparing the densities of the liquid unbranched alkanes and cycloalkanes: (Source) The cycloalkanes have slightly lower molecular mass than their parent unbranched alkanes with the same number of carbon atoms, yet ...


17

Tollen's reagent (ammoniacal silver nitrate) reacts with terminal acetylenes to form the silver acetylide which precipitates out of solution $\ce{RC ≡ CH + AgNO3 + NH4OH→ RC ≡ CAg↓ + NH4NO3 + H2O}$ In the case of acetylene itself, since both ends of the molecule are (if you will) terminal acetylenes, a bis-silver acetylide salt is formed and precipitates ...


16

The $\mathrm{p}K_\mathrm{a}$ of acetylene is $25$. It is very weakly acidic, and hence, $\ce{KOH}$ is not sufficiently alkaline to react with it. Even methanol, with a $\mathrm{p}K_\mathrm{a}$ of $15.5$ does not react much with hydroxide ion. On other hand, $\ce{NaH}$ or $\ce{NaNH2}$ have more basic anions than hydroxide, and weak acids such as acetylene or ...


16

Higher $\mathrm{RON}$ seems possible. Yet the boiling point rises accordingly while heat of combustion remains roughly the same. Here are two compounds that fit all posed criteria. \begin{array}{|c|c|c|c|c|} \hline \mathbf{Molecule} & \mathrm{mp\ \mathrm{(^\circ C)}} & \mathrm{bp\ \mathrm{(^\circ C)}} & \Delta_\mathrm cH_\mathrm m^\circ\ (\...


15

Yes, it can be done by mimicking the conditions in the earth's mantle. It was shown by Alexander Goncharov and coworkers [1] by placing methane in a diamond anvil cell, applying a pressure of more than 2 GPa and heating everything to a temperature around 1000-1500 K with a laser. Is it economical? Hardly, but very interesting anyway! Kolesnikov, A.; ...


13

The current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book) reads as follows: P-44.1.2.2 Systems composed of rings and chains (exclusive of linear phanes) Two methods are recognized to name systems composed of rings and chains (exclusive of linear phanes). (1) Within the same class, a ...


13

What I usually do when I start numbering is look for branching and start numbering at the end with the closest branch. Also, keep in mind that with branching you'll want to consider numbering from one of the branches (if it'll yield a long chain.) I'm using the structure you made as an example: Here I numbered from the side with the most branching. But ...


13

The IUPAC recommendations on this matter have been changed. In the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book), the order of seniority between unsaturation and length of chain given in earlier recommendations is reversed: (…), the first criterion to be considered in choosing a preferred ...


13

I agree with the points made above regarding attractive forces in the liquid being diminished in the gas phase. However, I also think there may be an entropic component to all of this. When a molecule undergoes a phase change from liquid to gas (e.g. it boils) $$\Delta G_\mathrm{vap} = \Delta H_\mathrm{vap} - T_\mathrm{vap} \times \Delta S_\mathrm{vap} = ...


13

If you want to consider the diene as the main chain, you could call this 2-cyclohexyl-1,3-butadiene. This used to be the proper name for the compound, as double bonds used to take priority over any length of a carbon chain in IUPAC nomenclature. This compound exists, and you could theoretically purchase it at some place like this. In recent years, the proper ...


13

You have asked quite a number of questions in your post so let's tackle it one by one. Why does the oxidation take place at that particular nitrogen atom? To understand this, we first need to acknowledge that peroxyacids $\ce {RCO3H}$ are electrophilic oxidising agents. Specifically, the oxygen atom attached to the $\ce {H}$ is the electrophilic atom. ...


13

If it doesn't specifically need to be a hydrocarbon, zinc metal melts at 419.5 °C. Could you do an "ice bath" of zinc chunks in molten zinc, maintaining the melt right at its melting point?


12

Azulene has a 1.05 debye dipole moment, A hydrocarbon as such bonded as an isolated cation-anion pair with no heteroatoms could happen in principle given sufficient steric hindrance. Penta-tert-butylcyclopentadienide or pentakis(2,4,6-tri-tert-butylphenyl)cyclopentadienide with like fully substituted cyclpropenium or tropylium might work. Similar ...


12

Hydrocarbons are in fact the main source of hydrogen gas. According to Wikipedia, 95% of all hydrogen is produced by the steam reforming reaction: $$\ce{CH4(g) + H2O(g) -> 3H2(g) + CO(g)}$$ This is a very important industrial process which has been studied in depth. It is done at very high temperatures (~1000 °C) and under pressure (~20 atm), and can be ...


12

Fascinating molecule. I am not offering anything substantially, new or original here; merely here to confirm what has already been said. I couldn't find any evidence that suggests this particular molecule has been synthesised. In particular, I wonder if the five outer rings would be exactly perpendicular to the center one (eclipsed), or somewhat ...


12

The person in the video said it was about $\pu{45^oF}$. At this temperature propane has a vapor pressure of about 8 atm, so that is the pressure that built up inside the Coke bottle. Once this pressure had built up, it quit boiling. The fact that he could still fairly easily squeeze the bottle suggests that it was probably not very close to bursting from ...


11

"Ionic bond" does not necessarily mean the same thing as "bond that is not covalent". For example, I would have a difficult time classifying a hydrogen bond as being either ionic or covalent in nature. Nevertheless, four different hydrocarbon salts (i.e. salts containing only carbon and hydrogen) have been reported by Okamoto et al. (J. Org. Chem. 1990, 55 (...


11

You're right in thinking that it's an alkane. Now I think I shouldn't blame you for getting confused by $\ldots$ as a molecular formula which is mainly used in cars as fuel $\ldots$ Because First off, we don't know if $x$ in the molecular formula is an integer or a decimal number. Second, we don't know what fuel is meant. It's just supposed to be a ...


11

Your observation that unsaturated hydrocarbons burn with a sooty flame is not always true and depends on the circumstances. There are more factors at play than the nature of the hydrocarbon that is burning. The most important reason why flames are sometimes smoky is that the combustion is incomplete. This means that not enough oxygen was present to fully ...


11

There are a few problems with what you're proposing: The reaction requires energy. Where do get the methane from? What will you do with the carbon you're generating? The energy problem can be solved by using surplus energy from renewable source like solar and wind, but, as airhuff also mentiond in a comment, there is much more CO2 in the atmosphere than ...


10

These are both aromatic, but only one is flat. Added: The molecule on the right is not flat because of the 2 hydrogens overlapping.


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