Properties of organic compounds Flashcards
What are physical properties influenced by? (4)
- size
- structure
- shape
- degree of polarisation
What are dispersion forces?
When electrons are momentarily distributed unevenly in the molecule; inducing a temporary dipole.
Strength influenced by size and shape.
What are dipole-dipole bonds?
When two atoms have an unequal sharing of electrons due to a difference in electronegativity.
Creates a partial charge on a dipole.
What is hydrogen bonding?
When a molecule contains a hydrogen atom which is bonded to F, O, N.
Strong bond due to a larger dipole as electronegative atoms attract H atoms electrons leaving its nucleus exposed. This allows other atoms to come much closer to bond.
What is a structural isomer?
Has same molecular formula, but different structural formula.
What is a stereoisomer?
When two or more compounds differ only in the spatial arrangements of their atoms.
What are the two types of stereoisomers?
Enantiomers and geometric isomers.
What is a geometric isomer?
Has the same structure but a different geometry due to a restricted rotation.
- occurs on double or triple bonds
- can be CIS or TRANS
How does the geometry of isomer affect its properties? (3)
- in solids, the spacial arrangements affect the boiling point
- trans pack more closely in solids
- the polarity can be different and therefore affect BP and solubility
What is an enantiomer?
Chiral molecules that are non-superimposable on their mirror image.
Have 4 different groups attached to the chiral carbon.
How are enantiomers properties affected? (2)
- optical properties
- biological properties
What is a chiral molecule?
When there are 2 or more different groups attached to the tetrahedral atom.
What is an achiral molecule?
When there are 2 or more groups attached to the tetrahedral atom that are the SAME.
What are the properties of structural isomers?
Different chemical, physical and biological properties
- Chained isomers have a higher boiling point than
branched
- position of functional grp affects compactness + polarity
- functional groups can affect the intermolecular forces
What are the types of structural isomers? (4)
- chain isomers
- branched isomers
- positional isomers
- functional isomerism
What are the properties of alkanes?
- colourless
- less dense than water
- weaker intermolecular forces
- non-polar
- insoluble in water
- flammable
What properties of alkanes change with chain length?
- intermolecular forces increase
- viscosity increases
- boiling point increases: chains become entangled
- non-polar increases: outweighing polar regions
What are the properties of alkenes and alkynes?
- more reactive than alkanes: higher e- density at bonds
- double/ triple bond limits rotation
- unstable
- flammable
- decolourises bromine
What are the properties of alcohols?
- ability to form hydrogen bonds
- high boiling point
- solubility decreases with chain length ( np region weighs out p region)
- flammable
- usually clear liquid
What are the properties of carboxylic acids?
- ability to form hydrogen bonds
- high bp (very strong h bonds)
- soluble in water
- weak acid
What are the properties of aldehydes and ketones?
- volatile
- solubility decreases with chain length
- high bp due to polarity
What are the properties of esters?
- sweet smelling liquid
- slightly soluble in water
What are the properties of amines?
- very stable
- odorous
- can act as a weak base
- form H bonds (weak)
- solubility decreases with chain length ( np region weighs out p region)
- bp lower than alcohol
What are the properties of amides?
- high boiling point (due to forming multiple h bonds)
- solubility decreases with chain length
