Organic chem: Haloalkanes Flashcards
How are haloalkanes named?
The halogen is treated as a substituent to the alkane scaffold
As with alkanes, substituents are ordered alphabetically
The halogen can be covalently attached to a primary, secondary or tertiary carbon
Do halogens have a higher or lower electronegativity than carbon?
Higher electronegativity
Why are covalent bonds between carbon and halogens polar?
The electrons are not equally distributed between the two atoms
What are stereoisomers?
Isomers whose atoms are connected in the same order, but their spatial arrangement differs
When is a carbon compound chiral?
A carbon compound is chiral if at least one carbon is bonded to four different atoms or groups
What does chiral mean?
Asymmetric so that the structure and its mirror image are not superimposable
What is a stereocentre/ asymmetric carbon?
A chiral carbon atom
What is an enantiomer?
Pair of chiral molecules
What is a racemate/ racemic mixture?
A 1:1 mixture of enantiomers
What is the problem with racemic mixtures when creating drugs?
Many drugs are chiral, with only one enantiomer possessing the desired properties
Opposite enantiomer may be biologically inactive, active in a different way or produce undesirable side effects
E.g. thalidomide
What does enantiomerically pure mean?
Chiral molecules present as single enantiomers
What are diastereoisomers?
Stereoisomers that are not mirror images
What two reactions do haloalkanes commonly do?
Nucleophilic substitution
Elimination
What is a nucleophile?
A chemical species that donates an electron pair
What are the two mechanisms for nucleophilic substitution?
- Sn1 Leaving group goes first, nucleophile comes in later: Heterolytic dissociation
- Sn2 Leaving group goes and nucleophile comes in at the same time: direct displacement
