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Chemistry 4 > Properties of organic compounds > Flashcards

Properties of organic compounds Flashcards

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1
Q

What are physical properties influenced by? (4)

A
  • size
  • structure
  • shape
  • degree of polarisation
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2
Q

What are dispersion forces?

A

When electrons are momentarily distributed unevenly in the molecule; inducing a temporary dipole.
Strength influenced by size and shape.

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3
Q

What are dipole-dipole bonds?

A

When two atoms have an unequal sharing of electrons due to a difference in electronegativity.
Creates a partial charge on a dipole.

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4
Q

What is hydrogen bonding?

A

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.

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5
Q

What is a structural isomer?

A

Has same molecular formula, but different structural formula.

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6
Q

What is a stereoisomer?

A

When two or more compounds differ only in the spatial arrangements of their atoms.

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7
Q

What are the two types of stereoisomers?

A

Enantiomers and geometric isomers.

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8
Q

What is a geometric isomer?

A

Has the same structure but a different geometry due to a restricted rotation.

  • occurs on double or triple bonds
  • can be CIS or TRANS
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9
Q

How does the geometry of isomer affect its properties? (3)

A
  • 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
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10
Q

What is an enantiomer?

A

Chiral molecules that are non-superimposable on their mirror image.
Have 4 different groups attached to the chiral carbon.

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11
Q

How are enantiomers properties affected? (2)

A
  • optical properties

- biological properties

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12
Q

What is a chiral molecule?

A

When there are 2 or more different groups attached to the tetrahedral atom.

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13
Q

What is an achiral molecule?

A

When there are 2 or more groups attached to the tetrahedral atom that are the SAME.

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14
Q

What are the properties of structural isomers?

A

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

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15
Q

What are the types of structural isomers? (4)

A
  • chain isomers
  • branched isomers
  • positional isomers
  • functional isomerism
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16
Q

What are the properties of alkanes?

A
  • colourless
  • less dense than water
  • weaker intermolecular forces
  • non-polar
  • insoluble in water
  • flammable
17
Q

What properties of alkanes change with chain length?

A
  • intermolecular forces increase
  • viscosity increases
  • boiling point increases: chains become entangled
  • non-polar increases: outweighing polar regions
18
Q

What are the properties of alkenes and alkynes?

A
  • more reactive than alkanes: higher e- density at bonds
  • double/ triple bond limits rotation
  • unstable
  • flammable
  • decolourises bromine
19
Q

What are the properties of alcohols?

A
  • ability to form hydrogen bonds
  • high boiling point
  • solubility decreases with chain length ( np region weighs out p region)
  • flammable
  • usually clear liquid
20
Q

What are the properties of carboxylic acids?

A
  • ability to form hydrogen bonds
  • high bp (very strong h bonds)
  • soluble in water
  • weak acid
21
Q

What are the properties of aldehydes and ketones?

A
  • volatile
  • solubility decreases with chain length
  • high bp due to polarity
22
Q

What are the properties of esters?

A
  • sweet smelling liquid

- slightly soluble in water

23
Q

What are the properties of amines?

A
  • 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
24
Q

What are the properties of amides?

A
  • high boiling point (due to forming multiple h bonds)

- solubility decreases with chain length

25
Q

What molecule will have the highest melting point?

A
  • the largest molecules
  • presence of polar functional groups
  • ability to hydrogen bond
  • small degree of branching
    Highest intermolecular forces operating between them leads to the highest melting point
26
Q

What molecule will have the highest viscosity?

A
  • longest chain
  • presence of polar functional groups
  • ability to hydrogen bond
  • small degree of branching
    The longest chains and highest intermolecular forces result in the most viscous liquid.
27
Q

What molecule would be the most volatile?

A

The most volatile compounds will have the lowest boiling point.
Although pentane and methylbutane have the same molecular formula, due to branching methyl butane molecules cannot pack as closely together resulting in a slightly lower boiling point than pentane.

28
Q

What is viscosity?

A

The resistance of a liquid to flow.

29
Q

What is flashpoint?

A

Lowest temp at which it can vaporise to form a mixture that will ignite in air.
As boiling point increases the flash point will also increase.

30
Q

Which of the two compounds, propane or propan-1-ol, would be expected to have the higher boiling point?

A

Propan-1-ol contains the polar O-H bond which will allow it to hydrogen bond to other propanol molecules. This is a stronger form of intermolecular bonding resulting in a higher boiling point.

31
Q

Compare and contrast aldehydes and ketones?

A

Both aldehydes and ketones have a C=O (carbonyl group) in their functional group.

32
Q

What determines if a bond is stable?

A

A higher bond strength which requires more energy to break the bond.

33
Q

What is bond energy and how does the number of bonds affect this?

A

Bond energy is a measure of the strength of a chemical bond.

A higher number of bonds means that there is a higher electron density in bond, thus more bonds = higher bond energy.

Chemistry 4 (7 decks)

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