Organic chemistry
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This blog is a learning resource for undergraduate students studying organic chemistry. It consists of a database of actual questions and answers about organic chemistry collected by a chemistry professor teaching the subject.
Organic chemistry
4M ago
Can you re-explain why nucleophilicity does not correlate with basicity under protic conditions? (Because the larger particle size decreases their basicity and nucleophilicity due to stabilization and increases nucleophilicity due to polarization. In protic solvents the basicity is suppressed, but nucleophilicity is not affected, so polarization overrides stabilization. Great question! I added it to our organic chemistry blog. - GS).  ..read more
Organic chemistry
1y ago
Can you clarify the differences between nucleophilicity (Nucleophiles change their ability to donate a pair of electrons in the process of the reaction due to polarizability. They usually attack carbon - GS)., basicity (Bases do not change their ability to donate a pair of electrons in the process of the reaction. They usually attack carbon - GS), and polarizability (Ease of separation of charges in the electric field, which makes the difference between bases and nucleophiles - GS ..read more
Organic chemistry
1y ago
For which reactions do we use markovnikov’s rule versus anti-markovnikov’s rule? (Regardless of the rule, the preferred reaction proceeds through the most stable cation or radical on the most substituted carbon. It requires the least substituted carbon of the C=C bond to be attacked. So, when the attacking particle is hydrogen (such as H+ in acid-catalyzed hydration or hydrohalogenation) or something that will become hydrogen later (Hg(OAc)2 in mercuration followed by reduction, the reaction goes by Markovnikov rule. If the least substituted carbon is attacked with something else (Br. in ..read more
Organic chemistry
3y ago
How can you tell when a reaction goes through the meisenheimer complex or benzyne? (The Meisenheimer complex is formed only in the presence of a resonance acceptor in an ortho- or para-position to the leaving group. Otherwise the reaction requires a strong base, harsher conditions, and proceeds through benzyne - GS ..read more
Organic chemistry
3y ago
Can you explain in more detail the separation of enantiomers into diastereomers? (A mixture of enantiomers is treated with a chiral reagent to convert them to two new compounds, which have opposite centers from enantiomers and same centers from the chiral reagent, so they are diastereomers. Next, the diastereomers are separated and cleaved back into original enantiomers and the chiral reagent back. - GS ..read more
Organic chemistry
4y ago
What should we know regarding fluorescence? I recall discussing the topic in the past but am unable to find my notes regarding. (When a molecule absorbs the energy of light, it can cause a chemical reaction (photochemistry), or re-emit back as a light of different energy (fluorescence), or “wiggle out” by molecular vibrations to heat. Rigidity of a molecule reduces “wiggling out” the energy, which increases the efficiency of fluorescence. Therefore, we can control fluorescence by affecting the molecule by pH, presence of metals, DNA, etc. That is how many chemical sensors work. - GS ..read more
Organic chemistry
4y ago
E1 reactions are not stereoselective, so would the products be present in a racemic mixture like Sn1? (No. Unlike SN1, E1 does not produce a chiral center because the C=C bond is planar. - GS ..read more
Organic chemistry
4y ago
So would the addition of acetic anhydride to an amine be acylation? (Yes. It is actually acyl nucleophilic substitution, because half of the anhydride molecule leaves. - GS). Also are there the same issues with acylation as there are with alkylation when trying to make a primary amine or not because acylation is substitution? (No. The C=O group in an acyl blocks the lone electron pair on nitrogen from the second acylation. That is why acylation can be used as a get-around way to avoid the issue with multiple alkylations. Example - Gabriel synthesis. - GS ..read more
Organic chemistry
4y ago
Why would the hydrogens attached to the carbons in an ether and amine not be able to be hydrogen bond donors? (The small difference in electronegativity between C and H leads to the low polarity of the C-H bond, which leads to a very small positive charge on H, so it does not interact with the lone electron pair of the H-bond acceptor efficiently. - GS ..read more
Organic chemistry
4y ago
For ortho meta para directors, it is the group that is already attached to the ring that “tells” the group that is adding where to go or is it the group that is adding that knows where to add “on its own”? (The group, which is already in the ring, because it participates in the stabilization of the intermediate sigma-complex. The incoming group is separated from the positively charged conjugated system of the sigma-complex by an sp3-carbon, so its influence is minimal ..read more