Why are SN2 reactions better in aprotic? (Poor solvation of the nucleophile favors SN2, while poor solvation of the leaving group disfavors SN1. - GS). Are both Sn2 and Sn1 reactions better in polar vs nonpolar? (Yes. Polarity helps formation of a carbocation (for SN1) and helps to dissolve the nucleophile (for both SN2 and SN1). - GS).
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.
Topics
- Halides-alcohols-ethers (94)
- Conjugation (60)
- Alkenes-alkynes (51)
- Carboxylic acid derivatives (39)
- Structure-bonding (39)
- Aldehydes and ketones (36)
- Alkanes-cycloalkanes (31)
- Stereochemistry (27)
- Spectroscopy (21)
- Acids-bases (19)
- Amines (18)
- Useful links (2)
Monday, March 26, 2018
Wednesday, March 21, 2018
Tuesday, March 13, 2018
Tuesday, February 13, 2018
Will you please explain the difference between cationic polymerization of alkenes and free radical polymerization of alkenes. And how that compares to addition of HCl to alkenes. (Both cationic polymerization and electrophilic addition of HCl start from protonation of C=C. Radical polymerization starts from the attack of C=C by a free radical. - GS).
I was reviewing through the lecture slides and came across the following question: Why do we not consider absorption of IR by N2 and O2, which are way more abundant in the atmosphere, then CO2? Is the answer because N2 and O2 are symmetrical, unlike CO2, and therefore they have a negligible dipole moment; and, with IR absorption such as in IR spectroscopy, a dipole moment must be present in order for IR to be absorbed? Thank you. (Almost. We need to consider change of the dipole moment, not the dipole moment itself. - GS).
How would the free-radical addition of Br-Br to cyclohexene compare to the non-free radical addition? (Under free-radical conditions, Br2 will substitute an allylic hydrogen rather than add to C=C. NBS is even a better reagent for free radical halogenation. - GS). Why does it substitute an allylic hydrogen instead of adding to the C=C? (Because abstraction of an allyl hydrogen leads to a stable allyl radical, so the reaction pathway shifts to the more favorable substitution over addition. Some addition still takes place, and this is suppressed by using NBS instead of Br2. - GS).
Sunday, February 11, 2018
Should we be able to predict carbocation rearrangements, or just know how/why they occur? (Yes., You can predict the rearrangement, if there is a pathway to a more stable carbocation by the following mechanism: http://ochem.orgfree.com/rear.html - GS.
Monday, January 29, 2018
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