isomers(organic chemistry) Flashcards
Define isomers.
Isomers are molecules with the same molecular formula but different arrangements of atoms.
Describe the two main categories of isomerism.
The two main categories of isomerism are structural isomers and stereoisomers.
Explain structural isomers.
Structural isomers are molecules that have the same atoms but different connections.
What are stereoisomers?
Stereoisomers are molecules that are connected in the same way but have different spatial arrangements of atoms.
List the three sub-types of structural isomers.
The three sub-types of structural isomers are chain isomers, positional isomers, and functional group isomers.
How do chain isomers differ from each other?
Chain isomers differ in the arrangement of the carbon skeleton, such as straight chain versus branched chain.
Define positional isomers.
Positional isomers are isomers where the functional group is attached at different carbon atoms.
What are functional group isomers?
Functional group isomers are isomers where the atoms form different functional groups.
Identify the molecular formula of butane.
The molecular formula of butane is C4H10.
Describe the possible structures of butane.
Butane can exist as a straight chain of four carbon atoms or as a branched chain known as methylpropane.
How many chain isomers does butane have?
Butane has two chain isomers: butane and methylpropane.
Explain the process of identifying chain isomers using butane as an example.
To identify chain isomers of butane, first determine its molecular formula (C4H10), then explore possible structures, which include a straight chain and a branched chain.
Determine the positional isomers of chloropentane.
The content does not provide specific details on the positional isomers of chloropentane.
Identify the molecular formula of chloropentane.
Chloropentane has the molecular formula C5H11Cl.
Describe the possible structures of chloropentane.
The possible structures of chloropentane are 1-chloropentane, 2-chloropentane, and 3-chloropentane.
Explain why 4-chloropentane and 5-chloropentane are not distinct isomers.
4-chloropentane and 5-chloropentane mirror 2-chloropentane and 1-chloropentane due to the symmetry of the pentane chain.
Define functional group isomers for C3H6O.
C3H6O can form functional group isomers such as aldehydes and ketones.
How many functional group isomers does C3H6O have, and what are they?
C3H6O has two functional group isomers: propanal (an aldehyde) and propanone (a ketone).
Describe the two sub-types of stereoisomers.
Stereoisomers are categorized into geometric (E/Z) isomers and optical isomers.
Define Z-isomer in terms of molecular arrangement.
Z-isomer is when higher priority groups are on the same side (above or below) of the double bond.
Define E-isomer in terms of molecular arrangement.
E-isomer is when higher priority groups are across the double bond from each other.
Describe the arrangement of groups in Z-but-2-ene.
In Z-but-2-ene, the higher priority methyl groups are positioned above the same side of the double bond.
Describe the arrangement of groups in E-but-2-ene.
In E-but-2-ene, the methyl groups are positioned diagonally across the double bond from one another.
How do you identify E/Z isomers using priority rules?
Use Cahn-Ingold-Prelog priority rules to assign priority to groups bonded to each carbon of the double bond.
What determines the priority of groups in E/Z isomer classification?
Higher atomic number means higher priority when determining the arrangement of groups.
Explain the first step in classifying an alkene using E/Z terminology.
Examine the molecule to identify the double bond and the groups attached to the carbon atoms.
What is the second step in applying E/Z terminology to an alkene?
Apply Cahn-Ingold-Prelog priority rules to compare directly attached atoms to the double-bonded carbons.
How are the groups arranged in an alkene with an ethyl group and a hydrogen atom on one carbon, and a bromine atom and a fluorine atom on the other?
The arrangement needs to be analyzed to determine if it is E or Z based on the priority of the groups.
Define the relationship between atomic number and priority in molecular structures.
Higher atomic number means higher priority.
Describe the priority groups on the first carbon of a molecule.
The ethyl group (C) has a higher atomic number than hydrogen (H).
Identify the priority groups on the second carbon of a molecule.
Bromine (Br) has a higher atomic number than fluorine (F).
How are high priority groups arranged in the E-isomer?
The high priority groups (ethyl and bromine) are positioned on opposite sides of the double bond.
What is the significance of a chiral centre in optical isomers?
A chiral centre is a carbon atom bonded to four different substituents, creating non-superimposable mirror image forms, or enantiomers.
Give an example of a molecule with a chiral centre and its substituents.
2-chlorobutane has a chiral centre on its second carbon, bonded to a chlorine atom, a methyl group, an ethyl group, and a hydrogen atom.
Explain the concept of enantiomers in optical isomers.
Enantiomers are two mirror image forms of a molecule that are structurally identical but show different interactions with plane-polarised light.
How do optical isomers interact with plane-polarised light?
Optical isomers, or enantiomers, show different interactions with plane-polarised light despite being structurally identical.
