Questions tagged [organic-chemistry]
Use this tag for questions relating to organic molecules and their properties (structure of organic molecules, spectroscopic properties, reaction mechanisms, stereochemistry etc). DO NOT use this tag as the only tag in your question, as this tag by itself cannot appropriately classify your question. Always use this tag in addition to other more specific tags.
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Ortho-effect in substituted aromatic acids and bases
When comparing o,m,p-toluidine basicities, the ortho effect is believed to explain why o-toluidine is weaker. But when comparing o,m,p-toluic acid basicities, the ortho effect is stated as a reason ...
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What is the reason for the exceptional stability of the cyclopropylmethyl carbocation?
Can someone explain this to me by drawing resonance structures for the cyclopropylmethyl carbocation please?
Also one more question, is the tricyclopropylmethyl carbocation more stable than tropylium ...
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Why does cyclopropane react with bromine?
In my exam, I was asked why cyclopropane could decolourise bromine water (indicating that it reacted with the bromine).
All I could guess was that it is related to the high angle strain in ...
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What is the perfect definition for chirality?
Why is chirality defined differently for organic and inorganic compounds?
Why are inorganic compounds deemed to be optically active if they have more than one of the same ligands attached to the ...
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IUPAC nomenclature: "Smallest sum of locants"?
While naming any compound, the numbering should be done such that position of substituted groups gives smallest sum.
I'm struggling with the IUPAC naming for cyclic compounds. How exactly does this ...
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Why are vinylic and arylic carbocations highly unstable?
I have checked the internet and read quite a few books, but I still am not able to understand why vinylic and arylic carbocations are highly unstable.
What I found while surfing the internet is: For ...
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How do you name an alkene using IUPAC rules if the longest carbon chain in this alkene does not include the double bond?
For example, which is the right way to name this compound:
Is it 2-bromo-4-methylenehexane or 4-bromo-2-ethylpent-1-ene?
Does the larger number of carbon in a chain take priority, as in the former, ...
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What makes C=O more stable that C(OH)₂
When there are $2$ hydroxy groups on same carbon, they tend to undergo dehydration ( of course with exceptions like chloral where $\ce H$ bonding prevails).
Why does this happen? We are breaking a ...
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Molecular chirality and optical rotation
Why does having molecular chirality result in optical rotation? The dissymetry or chirality of molecules translates to the rotation of plane polarized light, the magnitude and direction depending on ...
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How to determine number of structural isomers?
I have come across many questions where I'm asked to give the number of possible structural isomers. For example number, structural isomers of hexane is 5, while the number structural isomers of ...
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Relative acidities of alkanes, alkenes, and alkynes
How does one explain the trend in bond lengths and acidity of the following hydrocarbons?
$$\begin{array}{ccc}
\hline
\text{Species} & \ce{C-H}\text{ bond length / Å} & \mathrm{p}K_\mathrm{a} ...
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Mechanism of arene side chain oxidation by permanganate
When treated with hot, concentrated acidic $\ce{KMnO4}$, arenes are oxidised to the corresponding carboxylic acids. For example, toluene is oxidised to benzoic acid.
I've tried to examine how this ...
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What's the difference between a nucleophile and a base?
Obviously it depends on the context whether you would call a particular species a nucleophile or a base but are the two terms largely synonymous or is there a difference?
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What is the major product on chlorination of 2-methylbutane?
I came across a question asking for the major product on chlorination of 2-methylbutane. The answer in the back of the book says it will be 2-chloro-3-methylbutane. However, I thought the major ...
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Why does alcoholic KOH prefer elimination whereas aqueous KOH prefers substitution?
What is the basic difference between aqueous and alcoholic $\ce{KOH}$? Why does alcoholic $\ce{KOH}$ prefer elimination whereas aqueous $\ce{KOH}$ prefers substitution?
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Is pyrene aromatic despite failing Hückel's rule?
Pyrene doesn't seem to be aromatic. However, sources claim that it is aromatic.
Considerations:
Pyrene is cyclic. ✓
Pyrene is flat (planar). ✓
Pyrene has 16 π electrons.
Every atom in the ring ...
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Which carbocation is more stable, the ethyl- or 1-propyl-carbocation?
$\ce{C2H5+ vs \ C3H7+}$
There are two conflicting trends here.
Inductive effect of ethyl will be higher than that of methyl so carbocation attached to ethyl (3 carbons in total) should be more stable....
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Why is 2-methylpropene less in energy than its alkene counterparts?
Other isomers include 1-butene, cis 2-butene, and trans 2-butene. Why would 2-methylpropene be less in energy if there is more steric hindrance?
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Is cyclobutadiene antiaromatic?
Cyclobutadiene is very unstable. But, some sources claim that this instability can be attributed to other factors such as ring and angle strain rather than antiaromaticity.
According to some, ...
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How to rationalise the resonance structures and hybridisation of the nitrogen in a conjugated amine?
I was given the first structure, and then drew the other 5 resonance structures:
First of all, are they correct? ChemBioDraw had some complaints, but as far as I can see there's the same number of ...
user1160
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Why is acetic acid more acidic than phenol?
Acetic acid (ethanoic acid, $\mathrm pK_\mathrm a \approx 5$) is more acidic than phenol ($\mathrm pK_\mathrm a \approx 10$), which is reflected in their reactivity with a weak base such as sodium ...
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Stability of carbocations: CF3+ vs CH3+
Is $\ce{CF_3+}$ more stable than $\ce{CH_3+}$?
In $\ce{CF_3+}$, there is $\ce{C-F}$ back bonding that increases stability of the carbocations. But -I effect of $\ce{F}$ dominates +R effect and this ...
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Which is the more stable enol form?
If I understand correctly, when we go from a keto to an enol form, we simply abstract an alpha proton and thereby create a double bond to a carbon-bearing the hydroxyl functional group.
When ...
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Twisting stereoisomers with rings to determine R/S [closed]
I know that if the smallest atomic number group is not in the back, we can twist the molecule so that it is in the back and then determine if it is R/S (Left image). But if the chiral center is ...
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Is the ammonium substituent (-NH3+) really meta-directing in electrophilic substitution?
If we make a resonance structure for the anilinium ion, with positive charge at either the ortho or the para position, we get a pentavalent nitrogen, which is not possible. So, how is the $\ce{-NH3+}$ ...
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Explanation for the trends in nucleophilicity—Orbital interactions or electrostatic attraction
The trend of halide nucleophilicity in polar protic solvents is $$\ce{I- > Br- > Cl- > F-}$$
The reasons given by Solomons and Fryhle[1], and by Wade[2] are basically as follows.
Smaller ...
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What is Y-aromaticity? Is the trinitromethanide anion aromatic?
The wikipedia article on trinitromethane claims that:
There is some evidence that the anion (which obeys the $4n+2$ Hückel rule) is aromatic.
Unfortunately the citation is behind a paywall so I ...
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Addition of hydrogen bromide to 1,3-butadiene: thermodynamic and kinetic control
The reaction of one equivalent of hydrogen bromide with 1,3-butadiene gives different products at under different conditions:1
The addition of hydrogen chloride also gives rise to similar products.2 ...
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Thermodynamic vs Kinetic Sulphonation of Naphthalene
The left hand isomer is clearly the kinetically favoured product and the right hand isomer is the thermodynamically favoured product. However, I have no idea why. Can you explain?
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Is the ring or the chain chosen as the parent structure in octan-2-ylbenzene?
How would you name the above compound according to IUPAC rules? I see some sources say it is 2-phenyloctane, but ChemDraw and a few other sources say it is 2-octanylbenzene.
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Can heteroatoms with lone pairs be chiral centres?
If a compound has a carbon atom with four different groups covalently bonded to it, it is called asymmetric and enantiomers of the compound can exist.
But imagine if one has a different central atom, ...
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Migratory aptitude in Baeyer-Villiger reaction
In short, I do not understand how or why the migratory aptitude is as listed in every textbook I've read.
Firstly, they talk about a positive charge being built up that is stabilised by the movement ...
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Why do dianions (such as malonate) bind cations more strongly than anions?
Why does a dianion (such as malonate) bind cations more strongly than its equivalent anion (acetate)?
Is it simply because of the proximal availability of another $\ce{O-}$ group that can bind to ...
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Is there a general consensus on the causes of the alpha-effect?
There have been various explanations posited for the α-effect. The α-effect refers to a phenomenon wherein nucleophiles with lone pairs on atoms adjacent (i.e., in the α- position) to the atom bearing ...
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Rationalising the order of reactivity of carbonyl compounds towards nucleophiles
This is immediately following ron's answer from Why is a ketone more nucleophilic than an ester?
One of the most simplest questions you can ask, how can you rationalise the order of reactivity ...
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Is the t-butyl carbocation more stable than the benzyl carbocation?
Various authors have different views regarding stability order of the benzyl and t-butyl carbocations.
$$\ce{PhCH2+ ; (CH3)3C+}$$
In my opinion, resonance effect dominates, so the benzylic ...
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Is cis-1,2-dimethylcyclohexane a meso compound?
I was watching a video lecture today on hydrocarbons and came across this. The instructor says that, as there is a plane of symmetry, cis-1,2-dimethylcyclohexane is a meso-compound:
However, the ...
user14857
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Ring contraction in a carbocation due to ring strain and back bonding
Today our teacher told us that the following carbocation rearrangement occurs due to back bonding. I could not really follow what he meant. Can someone please explain what is actually happening during ...
user14857
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What is occuring on the quantum level when a molecule rotates plane polarized light?
What is occuring on the quantum level when a molecule rotates plane polarized light?
Also, why do enantiomers then rotate light in opposite directions? I would think that the electromagnetic waves ...
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IUPAC name for 1,2,3-trichlorocyclopropane?
What is the IUPAC name for the two isomers of 1,2,3-trichlorocyclopropane? Similarly what is the name for isomers of 1,2,3,4-tetrachlorocyclobutane, 1,2,3,4,5-pentachlorocyclopentane, etc?
1,2,3-...
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Can a organic compounds such as hydrocarbons contain an ionic bond?
Can organic compounds like hydrocarbons have types of bonds other than covalent bonds? Can they also possess ionic bonds?
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1,6-dimethylcyclohexene and 2,3-dimethylcyclohexene
Is there a difference between these two molecules?
If so how does one tell? What is the correct nomenclature for cycloalkenes? I know that the double bond is assumed to be between C1 and C2 but why ...
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Is (2R,3S)-butane-2,3-diol chiral?
Is the attached compound a chiral or achiral overall? My lecturer said that this is an achiral compound because it has a superposable mirror image but I don't get that. So I tried to figure out the ...
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In what way could benzoin give Tollen's test?
In Q29 of Joint Entrance Exam (JEE) 2016 India, the official answer key mentions that benzoin gives Tollen's test. However, I saw this post which says that it doesn't: Why do α-hydroxy ketones give ...
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What are the meanings of dotted and wavy lines in structural formulas?
So I came across this diagram,the other day:
As a chemistry student, I am well-versed with the dashed and wedged lines, but I was wondering what the wavy and the dotted line represent?
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Why is 1-ethylidene-4-methylcyclohexane chiral?
As far as I can tell, there doesn't seem to be a chiral carbon in the compound, 1-ethylidene-4-methylcyclohexane. The C-4 of the cyclohexane ring has two groups with exactly the same connectivity, and ...
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Why does the unstabilised Wittig reaction selectively form cis alkenes?
This question is meant for a simple unstabilised ylide.
The mechanism of the Wittig reaction, as given on ChemTube3d, involves a concerted formation of the oxaphosphetane (this is generally favoured ...
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Why does fructose reduce Tollen's reagent and Fehling's solution?
Even though fructose is a ketohexose (ketone-containing hexose, a six-carbon monosaccharide), it reduces Tollen's reagent and Fehling's solution. Generally, a ketone does not reduces Tollen's reagent ...
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Reaction of alcohols with PCl5 and PCl3
The reaction of alcohols $\ce{ ROH }$ with $\ce{ PCl5 }$ and $\ce{ PCl3 }$ yields an alkyl halide $\ce{RCl}.$ With $\ce{ PCl5 }$, the reaction is quite simple leading to the formation of $\ce{ RCl }$ ...
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Why are allenes chiral?
How is 1-bromo-3-chloropropa-1,2-diene ($\ce{BrHC=C=CHCl}$) chiral? It doesn't have any carbon that is connected to four different groups.
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