53 votes
Accepted

Why isn't ethane used for cooking?

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 ...
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39 votes

Why isn't ethane used for cooking?

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 ...
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  • 16.8k
36 votes

Five-pointed crown alkane C25H40: does it exist?

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]-...
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  • 65.8k
33 votes

Is pyrene aromatic despite failing Hückel's rule?

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 ...
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32 votes
Accepted

Is pyrene aromatic despite failing Hückel's rule?

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 ...
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  • 81.9k
24 votes
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Are geminal disubstituted alkenes more stable than their cis/trans isomers?

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 ...
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  • 2,107
22 votes
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Cyclobutadiene - Jahn–Teller effect or not?

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 ...
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  • 65.8k
22 votes
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Why doesn't liquid propane in a closed coke bottle burst?

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 ...
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21 votes
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Why do cyclic hydrocarbons have higher boiling points than their acyclic isomers?

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 ...
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21 votes

When I burn isopropyl alcohol (IPA), it burns orange. But when I burn ethyl alcohol, it burns totally blue. Why is this?

IPA has a different carbon:hydrogen ratio than ethanol. There is more incomplete combustion occurring with IPA, hence the smoky orange flame and smell of soot. Ethanol combusts more completely, ...
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20 votes
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Does acetylene give a positive Tollens' test? If not, why is this so?

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 v + NH4NO3 + H2O}$...
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  • 81.9k
18 votes

What single, pure compound would best replace petrol?

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|...
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18 votes
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ICHO Synthesis Problem 2018

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 ...
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18 votes
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When I burn isopropyl alcohol (IPA), it burns orange. But when I burn ethyl alcohol, it burns totally blue. Why is this?

Interesting observation. The blue flame color of all hydrocarbon fuels is due to the emission small diatomic carbon species such $C_2$ or CH. There is nothing magical about IPA having a yellow flame. ...
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  • 32.6k
16 votes
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Does the largest known cycloalkane contain 288 carbon atoms?

According to Makromol. Chem., Rapid Commun. 1985, 6 (3), 203–208[1], Kwang Sup Lee and Gerhard Wegner, attempting the synthesis and study of $n>100$, $\ce{C_nH_{2n}}$ cyclo-alkanes and linear ...
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15 votes

Conversion of methane to propane

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 ...
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14 votes

Is pyrene aromatic despite failing Hückel's rule?

While the previous answers are correct in indicating that pyrene has aromaticity, they are often correct for the wrong reason. The proper way to break down the aromaticity in pyrene is to make the ...
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  • 809
14 votes
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How can I draw 2,3-diethylheptane?

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 ...
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  • 6,326
14 votes
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400–430 degrees Celsius heated bath

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?
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  • 1,482
14 votes

Does motor oil get more viscous when heated & what is the meaning of the SAE motor oil code?

The numbers in the code have nothing to do with viscosity index. However, your understanding of 'W' for winter is correct. The real code for your car is actually SAE 5W-30 where SAE stands for the ...
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13 votes
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Is an SN1 reaction possible in halobenzene?

Yes, that reaction occurs, but generation of the phenyl carbocation was much more difficult than anyone might have guessed. Here is a drawing of the phenyl carbocation. First note that the 6 p ...
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  • 81.9k
13 votes

Why do cyclic hydrocarbons have higher boiling points than their acyclic isomers?

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 ...
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13 votes
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Is this molecule possible? And if so, what is it called? (Cyclic groups)

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 ...
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13 votes
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What is the mechanism of alkane combustion?

The following, very general radical reactions apply to any common combustion reaction of organic material. Details vary largely. Step 1 An energy spark of whatever kind turns triplet oxygen into its ...
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  • 11.4k
12 votes

Can a organic compounds such as hydrocarbons contain an ionic bond?

"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....
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  • 65.8k
12 votes

Conversion of methane to propane

Generally, this reaction is run in reverse. Hydrogen reformers are used to generate hydrogen by the following reaction scheme: $$\ce{CH4 + H2O -> CO + 3H2}~~~\mathrm{(Endothermic, 1000C)}$$ ...
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12 votes
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Is there a reaction to get hydrogen from hydrocarbons?

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 ...
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