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Relative stability of cis and trans cycloalkenes

Usually trans-olefins are more stable than their cis isomers for steric reasons, like you suggested. However in small and medium size rings this is not the case; here the cis-cycloalkene is more ...
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30 votes
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What is the perfect definition for chirality?

The correct definition of chirality is given in the IUPAC gold book as follows: chirality The geometric property of a rigid object (or spatial arrangement of points or atoms) of being non-...
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29 votes

Why is 2-methylpropene less in energy than its alkene counterparts?

There are two things we need to understand before we can answer the question. 1) More highly substituted double bonds are generally more stable than less substituted double bonds. This is because ...
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27 votes

What is the perfect definition for chirality?

I think Martin has provided an excellent answer, and I would like to supplement it with a few additional details and examples that might prove insightful. So as I already mentioned in the comments, ...
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26 votes
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How is exact racemization possible?

Racemization isn't "exact," but rather very very close to equality. It is just simple probability. Think of flipping a coin, p=probability for heads, and q=probability of tails. Now for a fair flip ...
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25 votes

How to determine number of structural isomers?

(1) As for the number of alkanes ($\ce{C_nH_{2n+2}}$), Table 1, which is extracted from the data reported in S. Fujita, MATCH Commun. Math. Comput. Chem., 57, 299--340 (2007) (access free), shows ...
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25 votes
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How to determine number of structural isomers?

It isn't easy but it is an interesting research topic Determining the number of possible structures for a given range of chemical formulae isn't simple even for saturated hydrocarbons. The number of ...
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21 votes
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Hydrocarbons with only 4 carbon atoms

Final update, all earlier edits incorporated. Groundrules: Considering compounds with: only carbon and hydrogen only 4 bonds to carbon There are 37 isomers without considering trans isomers; 49 ...
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17 votes
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Why do we insert a numeric multiplier after group positions when naming an isomer?

take 2,3-dimethylbutane In the case of different substituents on different or the same atom, we use a combination of the position and the name of the substituent, such as in 2-chloro-3-methoxy... 3-...
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16 votes
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Does knowing the ratio of masses of the elements in a compound lead to the unique chemical identity of the compound?

No, knowing the mass ratios is not sufficient by itself. In the absence of additional information (for example, molar mass) that would only be enough information to determine the empirical formula, ...
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14 votes

Why are conformational isomers considered as isomers?

Gaurang's answer deals well with the theory part I just wanted to give a visual aid. (Taken from Atropisomerism of naphthyl alcohol) Let's call the rotating substituent on the naphtahlene a fan. The ...
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14 votes

Is light a reactant in photochemical reactions?

It is neither reactant nor catalyst, and equilibrium concepts do not apply There are processes other than photochemistry that to go in a direction away from equilibrium. They require mechanical or ...
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13 votes
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How to calculate the number of geometrical isomers in allenes?

If we have one double bond in a hydrocarbon compound we have an olefin or alkene. Ethylene is the simplest example of this class of compounds. The carbons in the double bond and the 4 atoms attached ...
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13 votes

How is plane polarized light rotated by chiral compounds?

Circularly polarized light is like a helix that twists through space. The two components are mirror images of each other. Now, every molecule interacts with both the left-handed twisting light and the ...
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12 votes

Difference between Epimers and Diastereomers

This scheme I just drew up specifically for you should answer your question. Diastereomers are stereoisomers that are not enantiomers of each other. That includes conformers (geometric isomers that ...
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12 votes

Why are conformational isomers considered as isomers?

I was taught that geometric (cis-trans) isomers are considered isomers because there is a high energy barrier to breaking the double bond... There's a problem here. Geometrical isomers are isomers ...
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11 votes

Hydrocarbons with only 4 carbon atoms

How many different organic structures (from the pure theoretical viewpoint) can be drawed with only 4 (exact) carbon atoms and with/without hydrogen? We could make strict rules like each carbon ...
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11 votes

Isomers with molecular formula C₄H₇Cl

There are 12 different constitutional isomers: There is also the further possibility of stereoisomerism in some of the compounds above. 3: Two diastereomers (cis- and trans-) are possible. 7, 8, 9: ...
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11 votes
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Difference between Epimers and Diastereomers

epimers as compounds which differ by configuration at only one carbon Yes, at only one centre. However isn't that the same thing as diastereomers? No, not completely. Diastereomers differ at ...
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11 votes
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For molecules to be enantiomers, do the groups have to be non-superimposable mirror images even when rotated around C-C single bonds?

Real molecules surely do rotate around their single C-C bonds all the time(*). So yes, if two models can be superimposed after an internal rotation of such sort, this means they represent the same ...
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11 votes
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What is the reason of the color difference for the cis/trans isomers of tetraamminedichloridocobalt(III) chloride?

If you search a library for a copy of Inorganic Chemistry by Miessler and Tarr, they have an excellent diagram showing which explains the phenomenon. $\ce{Cl-}$ ligands have lone electrons that can ...
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11 votes
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What is the error in the number of aromatic isomers of C7H8O?

You are completely correct - the furan derivatives you've drawn display unquestionable aromatic character, though the "strength" of their aromaticity is somewhat lower than various other ...
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10 votes
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Predicting the products of the radical chlorination of propane

Let me give you two helpful hints. Propane If you use an internet search tool of your choice, you should quickly find out that propane is $\ce{C3H8}$, which has the structure $\ce{CH3CH2CH3}$. The ...
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