Orgo q's

[mag7ical]

1) What's the H NMR spectra of dimethyl ketone? I thought it was 2 singlets, but TopScore says it's not.

2) Can someone explain the difference between L and D amino acids? Which one is used in living things?

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[299678]

1. one singlet
2. L amino acid is used in living thing
all naturally occuring amino acids are L amino acid, just by convention, when we draw amino acid on fisher projection, we put amino group (NH2) on left side, so called L amino acid (L means simply left)
3. One more thing to remember is D sugar, all sugars digested by human is D sugar.

 

[Bio Dental Mom]

kpark is right, and dimethyl ketone only has one type of hydrogen, the one bound on the CH3's so that's the only signal you will get and since they are all the same you will get a high peak as well.

 

[orgohacks]

-the L means "levorotation" (left-rotating) - early last century, chemists discovered that solutions of natural amino acids rotate polarized light to the left (counter-clockwise). On the other hand, solutions of natural sugars rotated polarized light to the right ("dextrarotatory", or "right-rotating" in latin) - hence the D.
A handy thing to remember is that 19 of the 20 natural amino acids are (S) by the Cahn-Ingold-Prelog rules - the exception is cysteine, where the sulfur takes priority over the carbonyl (but is still an L-amino acid because it rotates light to the left).