Lab 6: OCHEM 1 |Reviewed Questions and Answers
In this experiment, what are we isolating? **** (S) - 1 phenylethylamine
How are we going to isolate it? **** Racemic (1) phenylethylamine will be reacted with
enatiomerically pure (2R,3R) tartaric acid to form diastereoisomeric salts which can be
resolved by selective crystallation from methanol
The isolated salt will be converted to the... **** optically active free base by treatment
with sodium hydroxide.
What do we use to determine to optical rotation of the product? **** Polarimeter, from
which we can determine the enantiomeric excess and evaluate the efficiency of our
resolution.
An object that has a non-superimposable mirror image is referred to as being **** chiral
Two non-superimposable mirror images are referred to as **** enantiomers
An equimolar mixture of two enantiomers is known as a **** racemic mixture
Enantiomers have identical ___ properties **** physical; solubility, melting point, boiling
point, etc.
How can isolate a single enantiomer from a racemic mixture? **** Chiral resolution.
What happens when a racemic mixture of 1-phenylethylamine is reacted with a single
enantiomer of tartaric acid? **** 2 diastereomeric salts form in a 1:1 ratio
What are the 2 diastereomeric salts formed? **** 1. (R,R) - tartaric acid salt (R amine)
and (S) amine, (R,R) tartaric acid salt.
Which salt is more soluble in methanol? **** R(amine): (R,R) tartaric acid salt
Since the (S) amine salt is less soluble, we are able to ___ out of a methanol solution
**** crystallize
Once the (S) amine is isolated, what do we treat it with and why? **** NaOH, it will
convert the salt to the free amine and disodium tartrate (neutralize it)
Samples that rotate light are said to be **** optically active
Specific rotation equation **** observed rotation / (concentration [g/mL]) x (pathlength
[dm, 1dm = 10 cm)
In this experiment, what are we isolating? **** (S) - 1 phenylethylamine
How are we going to isolate it? **** Racemic (1) phenylethylamine will be reacted with
enatiomerically pure (2R,3R) tartaric acid to form diastereoisomeric salts which can be
resolved by selective crystallation from methanol
The isolated salt will be converted to the... **** optically active free base by treatment
with sodium hydroxide.
What do we use to determine to optical rotation of the product? **** Polarimeter, from
which we can determine the enantiomeric excess and evaluate the efficiency of our
resolution.
An object that has a non-superimposable mirror image is referred to as being **** chiral
Two non-superimposable mirror images are referred to as **** enantiomers
An equimolar mixture of two enantiomers is known as a **** racemic mixture
Enantiomers have identical ___ properties **** physical; solubility, melting point, boiling
point, etc.
How can isolate a single enantiomer from a racemic mixture? **** Chiral resolution.
What happens when a racemic mixture of 1-phenylethylamine is reacted with a single
enantiomer of tartaric acid? **** 2 diastereomeric salts form in a 1:1 ratio
What are the 2 diastereomeric salts formed? **** 1. (R,R) - tartaric acid salt (R amine)
and (S) amine, (R,R) tartaric acid salt.
Which salt is more soluble in methanol? **** R(amine): (R,R) tartaric acid salt
Since the (S) amine salt is less soluble, we are able to ___ out of a methanol solution
**** crystallize
Once the (S) amine is isolated, what do we treat it with and why? **** NaOH, it will
convert the salt to the free amine and disodium tartrate (neutralize it)
Samples that rotate light are said to be **** optically active
Specific rotation equation **** observed rotation / (concentration [g/mL]) x (pathlength
[dm, 1dm = 10 cm)
