Section A: Non-Covalent Interactions Flashcards

(19 cards)

1
Q

Differences between covalent and non-covalent interactions

A
  1. Covalent have a shorter range
  2. Covalent are more highly directional
  3. Covalent more long-lasting
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2
Q

If more than 1 bond in a molecule is polar then

A

The overall molecular dipole, u, must be considered

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3
Q

The overall average interaction energy between freely rotating dipolar molecules is dependant on

A

The distance between them : E ~ - 1/r^6

and inversely dependant on temperature

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4
Q

How are non-polar molecules held together?

A

The electrons in a molecule can be polarised due to the influence of a polar molecule. The permanent dipole and induced dipole can then attract.

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5
Q

Dispersion Interaction

A

Fluctuating electron density can cause a instantaneous dipole in non-polar molecules that induce a dipole in neighbouring molecule. These induced dipoles attract

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6
Q

Polarisability

A

The size of a permanent dipole

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7
Q

Dielectric constant

A

Measured experimental values that determine how well a material stores electrical energy when exposed to an electric field -> property of the bulk substance

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8
Q

Generally more polar molecules have

A

Higher dielectric constants

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9
Q

When an ion is surrounded by polar molecules,

A

Many of their dipoles align in the field of the ion which lowers self-energy of ion

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10
Q

Why are H-bonds generally short ranged?

A

The formation of H bonds involves overlap of AO’s

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11
Q

Why are the properties of water anomalous?

A

Each water molecule can form up to 4 H-bonds with other water molecules, 2 as acceptors 2 as donors

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12
Q

The Grotthuss Mechanism

A

Conduction of H+ through water is an order of magnitude faster than conduction of similarly charged ions. This is because H bonds can become covalent bonds (visa versa) allowing transfer of charge from one location to another without diffusion of atoms.

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13
Q

In TLC, the mobile phase is driven by

A

Capillary forces

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14
Q

In TLC, affinity to stationary phase is dependent on

A

Strength of non-covalent interactions

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15
Q

Why do systems with H-bonds have high entropy?

A

There are many ways of arranging the H bonding network, each of the same energy

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16
Q

Hydrophobic molecules

A

Can’t form H-bonds -> reduces entropy

17
Q

The hydrophobic effect

A

Clustering of non-polar molecules due to entropically unfavourable interaction with water

18
Q

Amphiphile

A

Both hydrophobic and hydrophilic e.g. lipids

19
Q

Amphiphile self-assembly

A

Amphiphile’s self assemble in order to minimise the hydrophobic effect