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Biological Chemistry 1A > Bio-molecules basics > Flashcards

Bio-molecules basics Flashcards

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1
Q

Give the evidence for quantization of energy

A

When heat/electrical energy is applied to elements in gaseous form emission of radiation at discrete wavelengths is observed

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2
Q

What must the difference in electronegativity be for a bond to be considered covalent?

A

Less than 1.7

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3
Q

What are the difference in electronegativity be for a bond to be considered ionic?

A

Greater than or equal to 1.7

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4
Q

What must be true of electrons in a covalent bond?

A

For a covalent bond to be formed the number of electrons in a bonding orbital must be greater than the number of electrons in an anti-bonding orbital

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5
Q

Is an anti-bonding orbital higher or lower energy?

A

Higher

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6
Q

Is a bonding orbital higher or lower energy?

A

Lower

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7
Q

When are sigma bonds formed?

A

When one pair of electrons are shared between 2 atoms

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8
Q

What is a non-bonding orbital?

A

An orbital which contains a pair of electrons which is not undergoing bonding (e.g. a lone pair)

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9
Q

How is dependence of dispersion forces calculated?

A

1/r6

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10
Q

How can dispersion forces be maximised?

A

When opposing surfaces are complementary in shape

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11
Q

Over what kind of distance do dispersion forces act?

A

Close distances

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12
Q

How strong are dispersion forces?

A

Very weak

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13
Q

When are dipole-dipole interactions strongest?

A

When the molecules have permanent dipoles

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14
Q

How is dependence of dipole-dipole interactions calculated?

A

1/r6

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15
Q

What does the value of dependence represent?

A

The distance over which a force is effective over

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16
Q

Over what kind of distance is steric repulsion effective over?

A

very short distances

17
Q

What is the approximate dependence calculation for steric repulsion?

A

1/r12

18
Q

What is steric repulsion?

A

The repulsion atoms experience when brought very close together due to the negative charge electrons in the outer shell of atoms

19
Q

What forces do van der Waals forces take into account?

A
  • Dispersion forces
  • Dipole-dipole interactions
  • Steric repulsion
20
Q

What is the stereochemistry of the products of an SN2 reaction?

A

Produces 100% of one enantiomer

21
Q

What is the stereochemistry of the products of SN1 reaction?

A

Produces 50% of 1 enantiomer and 50% of the other enantiomer

22
Q

What is generally the rate limiting step of SN1 reactions?

A

The formation of the intermediate

23
Q

What is the stereochemistry of the products of SN2 reactions?

A

Inverted

24
Q

Compare the types of nucleophiles required for SN1 and SN2 reactions

A

Weak nucleophiles are needed for SN1 reactions whilst strong nuclephiles are needed for SN2 reactions

25
Q

What is the oxidation state of oxygen in peroxides?

A

-1

26
Q

What is bond length determined by?

A
  • atomic radii of atoms joined by the bond
  • type of covalent bond
27
Q

Why do double and triple bonds have shorter bond lengths?

A

Increased electron density affordsa greater attractive force on the nuclei of bonded atoms

28
Q

Do atomic orbitals exhibit the geometries predicted by VSEPR?

A

No

29
Q

How many electrons can an f orbital contain?

A

Up to 14

30
Q

Why is the arrangement of valence electrons as predicted by VSEPR?

A

Due to the hybridisation of atomic orbitals

31
Q

Which orbitals hybridise to form sp3

A

one s orbital and 3 p orbitals hydridise to form 4 sp3 orbitals

32
Q

What configuration do 4 sp3 orbitals produce?

A

Tetrahedral

33
Q

What are the 2 circumstances when there is restricted bond rotation of single bonds?

A
  • steric hindrance
  • Delocalised systems
34
Q

Why can mutiple bonds not rotate?

A

Rotating effectively disrupts the p-orbital overlap ‘breaking’ the pi bond whicn is energetically unfavourable

35
Q

When does diastereomerism occur?

A

When 2 or more stereoiosmers of a compound have different configurations at one or more of the equivalent stereocentres

36
Q

What is conformational isomerism?

A

A form of stereoisomerism in which the isomers can be interconverted exculsively by rotations about formally single bonds

37
Q

What is a rotamer?

A

Any of a set of conformers that arise from restricted rotation around a single bond

Biological Chemistry 1A (10 decks)

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