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S1 - Medicinal Chemistry > Molecular shape and Bonding > Flashcards

Molecular shape and Bonding Flashcards

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1
Q

what is a non- polar covalent bond ?

A

_ Similar electronegativity

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2
Q

what is a polar covalent bond ?

A
  • have dipoles
  • difference in electronegativity less than 2
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3
Q

what are 3 properties of ionic compounds ?

A
  • highly ordered crystal lattice
  • conduct electricity when molten
  • high bp
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4
Q

what are electropositive elements ?

A
  • elements with low ionisation energy (outer e- easily removed)
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5
Q

what are electronegative elements ?

A
  • elements that readily acquire electrons
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6
Q

what are the factors affecting lattice energy ?

A
  • ionic radius
  • ionic charge
  • no of shells /sheilding
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7
Q

How does ionic radius affect LE ?

A
  • smaller ionic radius = greater attraction so higher LE
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8
Q

How does ionic charge affect LE ?

A
  • greater ionic charge = greater attraction so higher lE
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9
Q

what is electronegativity ?

A
  • the ability of an atom to pull bonding electrons towards itself
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10
Q

what are degenerate orbitals ?

A
  • have same energy level
  • eg 2p orbitals
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11
Q

why do electrons in degenerate orbitlas occupy empty ones first ?

A
  • to minimise repulsion
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12
Q

why is the 4s orbital filled before 3d ?

A
  • it has a lower energy level
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13
Q

what is a radial node ?

A
  • region where there is zero probability of finding an electron
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14
Q

what are 2 properties of 2p orbitals ?

A
  • degenerate (same energy)
  • each orbital is perpendicular to the other two
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15
Q

what is the rule for molecular orbital theory ?

A
  • number of AO = number of MO
  • always get a bonding and anti-bonding MO
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16
Q

what is a sigma bonding molecular orbital ?

A
  • atomic orbitals of same phase sign overlap
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17
Q

what is anti-bonding molecular orbital ?

A
  • atomic orbitals of opposite phase sign overlap
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18
Q

what is constructive combination ?

A
  • wave function of e- are in the same phase
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19
Q

what is destructive combination ?

A
  • wave function of e- are in opposite phases
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20
Q

what is the difference between anti bonding and bonding MO ?

A
  • anti bonding has a node and no electrons
  • anti - bonding is higher in energy
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21
Q

What does end on overlap of 2p orbitals lead to ?

A
  • sigma bonds
22
Q

what does side on overlap of p orbitals lead to ?

A
  • pi bonds
23
Q

explain the hybridization of carbon for CH4 ?

A
  • one e- from a 2s orbital is promoted to a spare p orbital
  • makes 4 degenerate sp3 orbitals
  • helps from 4 equivalent bonds
24
Q

How are C-H bonds formed in ethane ?

A
  • overlap of sp3 and hydrogen s orbital
25
Q

How are C-C bonds formed in ethane ?

A
  • overlap of 2 carbon sp3 orbitals
26
Q

what is the bond angle for sp3 hybrids ?

A

109.5

27
Q

how is the c-c double bond formed in ethene?

A
  • sigma bond formed by overall of 2 carbon sp2 orbitals
  • Pi bond formed by side to side overlap of unhybridized p orbitals
28
Q

what is the bond angle and shape of sp2 ?

A

120 - trigonal planar

29
Q

what is the structure of ethyne ?

A
  • triple bond between carbons
  • each c attached to a H
30
Q

What is bond angle and shape of sp orbital ?

A
  • 180 - linear
31
Q

how many sigma and pi bonds are in a triple bond ?

A

2 pi bonds
1 sigma bond

32
Q

what is the shape + bonding in a methyl cation ?

A
  • CH3 +
  • sp2 hybridisation
  • trigonal planar - 120
33
Q

what is the bonding in a methyl radical ?

A

-CH3*
- sp2 hybridization
- trigonal planar - 120

34
Q

what is the shape + bonding in a methyl anion ?

A
  • three bonding pairs and 1 lone pair
  • sp3 hybridization
  • tetrahedral 109.5
35
Q

what is hybridisation of NH3 ?

A
  • 3 bonding pairs 1 lone pair
  • sp3 orbitals
  • bond angle is 107
36
Q

How is the C-N bond formed ?

A

sp3 - sp3 overlap

37
Q

hybridisation of H20 ?

A
  • sp3 oribitals
  • including lone pairs
  • 104.5
38
Q

What is the bonding in hydrogen halides ?

A

S-sp3

39
Q

Why is H-F bond stronger than HCI bond?

A

HF = 1s and 2sp3 orbital
HCl = 1s and 3sp3 orbital
CL bigger than F so less electron density in s-sp3
As size of X increases h-x bond gets weaker

40
Q

How does size of halide effect bond strength?

A

As size increases bond gets weaker + longer

41
Q

What are Van Der Waal forces ?

A
  • Weak interactions caused by momentary changes in e- density
42
Q

What is an intermolecular bond?

A
  • Between molecules
43
Q

What is an intramolecular bond?

A
  • Within a molecule
44
Q

What is the order of bond strength?

A

electrostatic forces Ionic bonds > H bonds > permanent dipole - dipole >
London forces

45
Q

What are the 2 conformations of alkanes?

A
  • Staggered + eclipsed
  • eclipsed the H are closer together
46
Q

Is staggered or eclipsed conformation more stable ?

A
  • staggered is more stable than eclipse , lower in energy
47
Q

what is torsional strain ?

A
  • repulsion of proximate bonding electrons
  • only found in eclipse conformation
48
Q

what is steric strain ?

A
  • atoms / groups too close to eachother so e - clouds repel
  • found in staggered or eclipsed
49
Q

what is angle strain ?

A
  • deviation from ideal tetrahedral bond angle
50
Q

which conformation of cyclohexane is more stable ?

A
  • chair conformation because no angular + torsional strain

S1 - Medicinal Chemistry (8 decks)

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