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Several days ago I offered a solution to the R/S assignment of the bridgehead carbons of (1R,2S,4R)-2-bromo-2-methylbicyclo[2.2.2]octane 1. During the middle of the night I realized that the method was faulty because the solution would not accommodate the (1S,2R,4S) enantiomer 3 but would rather predict (1R,2R,4R) which clearly is a non-existent ...


6

The first pair is not stereoisomers. You have correctly explain why. When you are dealing with stereoisomers, that's what you have to do first: Identify stereo centers. Accordingly, each compound of second pair has two stereo centers. Then, mark (R,S) configurations of all stereo centers. As I marked, the first compound has (R,S) configuration, while second ...


6

Your first set of compounds are identical. In the Fischer projection of a chiral centre, you can rotate three of the connected groups in a clockwise/anti-clockwise direction without changing the configuration of the chiral centre. Upon performing this operation (keeping the top fixed, rotating bottom three clockwise) on the first compound in the first set, ...


5

You can arrive at the answer without assigning R and S if you build a model or do some mental contortions. The conformation should be all-syn with respect to the atoms on the vertical axis (like it is for cyclic structures, e.g. sugars in the furanose or pyranose form). Then, you can simply read off which groups are on the left and on the right. In the ...


5

I used Jmol to make the following animated GIF: First I used NCBI's Pubchem Sketcher to get the SMILES code for the molecule: CC(C(C(C)F)(Br)F)O Then, I loaded it into JSmol running here using the load molecule by name button. Internally, this triggers the command load /*file*/"https://cactus.nci.nih.gov/chemical/structure/CC(C(C(C)F)(Br)F)O/file?...


5

According to Organic Chemistry: Second Edition,[1, pg 934](from which I assume that the question was taken): Enantiomerically pure (R)-2-bromopropanoic acid reacts with concentrated sodium hydroxide to give (S)-lactic acid. The reaction goes with inversion and is a typical SN2 reaction—and a good one too, since the reaction centre is adjacent to a carbonyl ...


2

The L and D nomenclature is directly transform from its origin, D- and L-phenylalanine. The following scheme summarize the transformation: The blue box in right-hand corner explains how L- and D-$\alpha$-amino acids get their names using Fischer projection (this is similar to D- and L-monosaccharides, replacing $\ce{OH}$ group by $\ce{NH2}$ group). If you ...


2

What is the general principle behind obtaining a optically pure mixture? (correct it as optically pure compound) You have too many separate questions. In short, organic chemists would tell you that there is full fledged branch of synthetic chemistry in which only one enantiomer is produced rather than a racemate. Read more about enantioselective synthesis, ...


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