Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86...
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Transcript of Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86...
![Page 1: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/1.jpg)
Intermolecular InteractionsIntermolecular Interactions
![Page 2: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/2.jpg)
Covalent Bond EnergiesCovalent Bond Energies
C-O bond 81 kcal/mol 1.43 Å
C-C bond 86 kcal/mol 1.54 Å
C-H bond 103 kcal/mol 1.11 Å
C=C bond 143 kcal/mol 1.33 Å
C=O bond 165 kcal/mol 1.21 Å
Compared to most non-covalent interactions these are:
• Very high energies
• Very short distances
• Highly dependant on orientation
![Page 3: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/3.jpg)
Intermolecular InteractionsIntermolecular InteractionsDriving Forces for the Formation of Supramolecular Structures
hydrophobic interaction <10 kcal/mol
electrostatic interaction ~5 kcal/mol
hydrogen bond interaction 2-10 kcal/mol
aromatic interaction 0-10 kcal/mol
van der Waals interaction 0.1-1 kcal/mol
The total intermolecular force acting between two molecules
is the sum of all the forces they exert on each other.
![Page 4: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/4.jpg)
Covalent bonding
Sharing of electrons to achieve stable electron configuration – Small difference in electronegativity of elements
– Bond energy – 50-100 kcal/mol
– Directional bond; between specific atoms in a specific direction, normally along the line connecting the two atoms that share a pair of electrons.
![Page 5: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/5.jpg)
Atomic Orbitals of Carbon
![Page 6: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/6.jpg)
d-orbitals f-orbitals
![Page 7: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/7.jpg)
sp3 hybridization and bond directionality
Shown together (large lobes only)
sp3
sp3
sp3
sp3
109.5o
Hybridizing s and three p orbitals form 4 identical sp3 orbitals
C
![Page 8: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/8.jpg)
sp3 hybridization of carbon orbitals
![Page 9: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/9.jpg)
sp2 hybridization of carbon orbitals
![Page 10: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/10.jpg)
sp hybridization of carbon orbitals
![Page 11: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/11.jpg)
Can be a very strong bond - even stronger then covalent bonds in some cases.
Can be an attractive or a repulsive force.
Non-directional force
Long range (1/r)
Highly dependant on the dielectric constant of the medium
+ -
A.A. Ion–Ion InteractionIon–Ion Interaction
![Page 12: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/12.jpg)
A.A. Ion–Ion InteractionIon–Ion Interaction
Energy = (k . z1 . z2 . e2) / (r12)
k = 1 / 4πo= Coulomb constant = 9 .109 N.m2/C2
e = elementary charge = 1.6 .10-19C
= dielectric constant
r12 = distance between the charges
The energy of an ion-ion interaction only decreases at a rate proportional to 1 / r. Therefore these are very long range forces.
![Page 13: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/13.jpg)
When designing a host / guest complex, what will be the energetic incentive for bringing two oppositely charged species to a distance of 3 nm of one another in water?
Energy = (k . z1 . z2 . e2) / (r12)
= 9 .109 . 1 . (-1) . (1.6 .10-19)2 / 78.5 . 3 . 10-9
= -2.3 . 10 -28 / 2.4 . 10 -7
= -9.8 . 10-22 J= -0.14 kcal/mol
A.A. Ion–Ion InteractionIon–Ion Interaction
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1 nm?
1 nm in Chloroform?
Energy = (k . z1 . z2 . e2) / (r12)
= 9 .109 . 1 . (-1) . (1.6 .10-19)2 / 78.5 . 1 . 10-9
= -2.3 . 10 -28 / 0.8 . 10 -7
= -29.4 . 10-22 J= -0.42 kcal/mol
= 9 .109 . 1 . (-1) . (1.6 .10-19)2 / 4.8 . 1 . 10-9
= -2.3 . 10 -28 / 4.8 . 10-9
= -4.79 . 10-20 J= -6.89 kcal/mol 8 % of a C-C bond
A.A. Ion–Ion InteractionIon–Ion Interaction
![Page 15: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/15.jpg)
B.B. Ion-Dipole InteractionIon-Dipole Interaction
Non-directional forces
Can be attractive or repulsive
Medium range interactions (1/r2)
Significantly weaker then ion-ion interactions
O
Na+
Example: crown ether complex with alkali metal ions
![Page 16: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/16.jpg)
Energy = -(k . Q . u . cos/ r2)
Maximum when = 0 or 180 degreesZero when = 90 degrees
u = q . l
u = dipole momentl = length of the dipoleq = partial charge on dipoler = distance from charge to center of dipoleQ = charge on ion
O
Na+
B.B. Ion-Dipole InteractionIon-Dipole Interaction
![Page 17: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/17.jpg)
Energy = -(k . Q . u . cos/ r2) If = zero= -k . Q . u / r2
= -9 .109 . 1.6 .10-19 . 2.9 . 3.336 .10-30 / r2
= -1.39 . 10-38 / 4.8 . (10-9)2
= -2.9 . 10-21 J= -0.42 kcal/mol
Example: Acetone pointing directly at Na+ ion ( = zero) at a distance of 1 nm (in chloroform)
B.B. Ion-Dipole InteractionIon-Dipole Interaction
![Page 18: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/18.jpg)
Intermolecular InteractionsIntermolecular Interactions interactions
– stacking (0 – 10 kcal/mol). Weak electrostatic interaction
between aromatic rings. There are two general types: face-to-face
and edge-to-face:
Face-to-face -stacking
interactions are responsible
for the slippery feel of
graphite. Similar -stacking
interactions help stabilize
DNA double helix.
![Page 19: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/19.jpg)
Intermolecular InteractionsIntermolecular Interactions interactions
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Intermolecular InteractionsIntermolecular Interactions interactions
Distribution of electron density in benzene molecule
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Edge-to-face
Intermolecular InteractionsIntermolecular Interactions Stacking
H
HH
H
H H
H
H
- -+
![Page 22: Intermolecular Interactions. Covalent Bond Energies C-O bond 81 kcal/mol1.43 Å C-C bond 86 kcal/mol1.54 Å C-H bond103 kcal/mol1.11 Å C=C bond143 kcal/mol1.33.](https://reader034.fdocuments.net/reader034/viewer/2022051622/5697bff91a28abf838cbf8db/html5/thumbnails/22.jpg)
Offset, face-to-face
HH
HH
HH
HH
Face-to-face, not favorable
Intermolecular InteractionsIntermolecular Interactions interactions