isomers Flashcards
whar are the 2 main classifications of isomers?
1) structural or constitutional isomers
-different atom-to-atom connections
2) sterioisomers
-same connection but different spatial arrangement
what is a regioisomer?
a structural isomer that has the same chemical formula as another compound, but a different structure
Why is chlorogenic acid significant in food chemistry?
Chlorogenic acids are a group of esters formed from caffeic acid and quinic acid
-they are major polyphenolic compounds found in coffee
-the isomers contribute to coffee’s complex chemical composition
What distinguishes stereoisomers from structural isomers? what are the types?
Stereoisomers have the same atom-to-atom connections but differ in the 3D arrangement of atoms. Types include geometrical isomers, diastereoisomers, and enantiomers
What are geometrical isomers? what classifications do they have?
Geometrical isomers differ in the arrangement around a double bond or ring
cis and trans
what are enantiomers? what must it include to be classified as an enantiomer?
Enantiomers are non-superimposable mirror images, such as left- and right-handed forms of molecules
-must be chiral
what are diastereoisomers?
non superimposable, non-mirror images
-they differ in some, but not all chiral centers
what is optical activity and what property causes this?
its the ability for a chiral compound to rotate plane polarized light
-the molecule must be chiral (non-superimposable mirror image with 4 different constituents)
How do enantiomers differ in their optical activity? what rotation correlates to what?
Enantiomers rotate light equally but in opposite directions:
Dextrorotatory (+): Rotates light clockwise
Levorotatory (−): Rotates light counterclockwise
What is Biot’s Law in the context of optical activity?
Biot’s Law relates the observed rotation to the specific rotation, path length, and concentration:
𝛼=[𝛼]t,λ⋅𝑙⋅𝑐
Where:
α = Observed rotation (in degrees).
[\α] = Specific rotation (degrees × dm²/g).
l = Path length of the polarimeter tube (in dm).
c = Concentration of the sample (g/mL).
How is specific rotation calculated?
What is a racemic mixture? Do racemic mixtures show optical activity? why or why not
A racemic mixture contains equal amounts of enantiomers
No, racemic mixtures contain equal amounts of both enantiomers, canceling out their rotations and making the mixture optically inactive
What is invert sugar, and how is it made? why is it important?
Invert sugar is a mixture of D-glucose and D-fructose made by hydrolyzing sucrose with acid or invertase. It changes optical rotation from positive (+66.5°) to negative due to the strong negative rotation of fructose (−93.8°)
It’s used in confectionery for its non-crystallizing properties and larger sweet taste
what is an epimer?
a type of diastereomer that only differs in configuration at one chiral center
what is the difference between the (d-/l-) (R/S) and (D-L) systems?
1) enantionmers are chatecorized based on their dextrarotary (d- / “+”) rotation or levoratatory rotation (l- / “-“)
2) R/S indicates the arrangement of atomical priority around a single carbon atom in diastereomers
3) The D/L system corresponds to the configuration of the whole molecule. It is an indication of where the OH group is on the highest numbered chiral carbon in sugars
what type of molecule are these structures?
enantiomers
what type of molecule are these structures?
epimers
what type of molecule are these structures?
diastereomer
what are the 4 kinds of sterioisomers?
1) conformational diasteriomers
2) conformational enationmers
3) configurational diasteriomers
4) configurational enantiomers
