Isomers Flashcards
What are configurational isomers?
Molecules with the same connectivity and atom-to-atom bonding sequence, but different arrangement in space Identical IUPAC names w/ additional prefix to indicate shape. E/Z Isomers are classifications of Configurational Isomers
What are the two key conditions for generating E-Z isomers on double bonds?
Different groups on each carbon of the double bond and two different groups on each carbon
What is a stereogenic carbon?
A carbon with four different groups attached, which can create a chiral molecule
What is the difference between cis and trans?
Relative terms describing the arrangement of groups on opposite or same sides of a ring or molecule
Why are molecular shapes important?
Molecular shapes determine interactions, especially in biological systems, affecting function and reactivity
What is an enantiomer?
Non-superimposable mirror images of a molecule with different spatial arrangements
What are diastereomers?
Stereoisomers that are not mirror images of each other, with different configurations but not identical
What are cis-trans diastereomers?
Isomers with different spatial arrangements on rings or double bonds, not interchangeable without breaking bonds
What are constitutional isomers?
Molecules with the same molecular formula but different atom connectivity and bonding sequence
What are conformational isomers?
Molecules with the same connectivity that can rotate around single bonds, creating different spatial arrangements (Same chemical + physical properties Identical IUPAC names)
What determines R/S classification of a stereogenic center?
Must be sp^3 carbon hybridised, tetrahedral in shape, mirror image (All characteristics of an Enantiomer), if the highest priority carbons are in order anti-clockwise: S classication—- clockwise: R
What makes a molecule chiral or achiral?
Chiral: Has a stereogenic center with four different groups
Achiral: Has symmetry or identical groups on a stereogenic center
What types of isomers are these?
Constitutional Isomers (Different IUPAC name, different atom-atom connectivity, same molecular formula)
What type of isomers are these?
Constitutional (right isomer is cis isomer too)
What type of isomers are these?
Conformational Isomer
What type of isomers are these?
Configurational (left is cis right is trans)
What are conformational isomers?
Molecules with the same chemical formula but different spatial arrangements, achieved through rotation around single bonds without breaking chemical bonds
What are the two extreme conformations for ethane? (Non-specific name)
Eclipsed (high energy, groups directly aligned) and Staggered (low energy, groups offset)
What determines the stability of a molecular conformation?
Energy level - lower energy conformations are more stable and occur more frequently
In a cyclohexane chair conformation, what are axial and equatorial positions?
Axial positions are vertical to the ring, equatorial positions are around the ring’s circumference
How do substituent group sizes affect positioning in cyclohexane?
Larger groups prefer equatorial positions (95% of the time) to minimize steric interactions and energy
What is the Newman projection used for?
To visualize molecular conformations by looking along a carbon-carbon bond, showing the arrangement of substituent groups
What conformer type is this?
Boat (Important to know that these have no equatorial or axial classifications)
What projection type is this and what is the conformer shape type?
Newman projection, non-eclipsing chair formation
