Term
List gravitational, nuclear, and electromagnetic forces for each category from smallest to biggest:
(A) Particle Size
(B) Distance
(C) Strength |
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Definition
(A) Nuclear, Electromagnetic, Gravitational
(B) Nuclear, Electromagnetic, Gravitational
(C) Gravitational, Electromagnetic, Nuclear |
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Term
| What are the borderline values of liberated energy and distance among atoms for strong and weak interaction? |
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Definition
Liberated energy: 40kJ/mol
Distance: 0.2nm |
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Term
| List 3 strong (bonding) interactions. |
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Definition
| Covalent bond, ionic bond (non-shielded), and coordination bond. |
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Term
| List 6 types of weak interactions. |
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Definition
| Charge-transfer interaction, Electrostatic Interactions (Keesom), Induced electrostatic interactions (Debye), Dispersion interaction (London), Hydrogen bond, hydrophobic interaction. |
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Term
| What are 2 types of electrostatic interactions? |
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Definition
| Ion-dipole and dipole-dipole. |
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Term
| All weak interactions are Van Der Waals interactions except... |
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Definition
| Hydrophobic interactions. |
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Term
| How does a covalent bond originate? |
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Definition
| The covalent bond originates between two atoms sharing two electrons of opposite spin. |
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Term
| Describe electron distribution in a covalent bond. |
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Definition
| Electrons are attracted to the more electronegative atom. |
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Term
| Covalent bonds are one of the strongest bonds. It has energy up to ________ and the distance between atoms is _________. It also has a ___________ directionality (angles between the bonds). |
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Definition
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Term
| List 2 examples of covalent bonds. |
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Definition
Hydrolysis of ester groups.
Binding of Beta-Lactams to bacterial cell wall enzymes. |
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Term
| What is a coordination bond? |
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Definition
| A covalent bond when the 2 shared electrons come from one interaction partner. |
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Term
| What is the interaction partner providing the electrons called? List some examples. |
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Definition
| It is called a ligand. It has a free electron pait, such as O, N, S, and halogens. |
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Term
| What is the interaction partner accommodating the electrons called? List some examples. |
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Definition
| It is called a central atom. It is almost always a transient metal which has vacant electron orbitals (Zn, Fe, Co...). They vacant orbitals are of different types (s, p, d) and hybridize to form unique bond geometries. |
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Term
| The number of ligand bonds alters the geometry of the molecule. List the geometry of each number of logan bonds possible, from 2-6. |
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Definition
2 - linear
4 - square planar
4 - tetrahedral
5 - trigonal bipyramid
6 - octahedral |
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Term
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Definition
| It is a totally polarized covalent bond where the 3 electrons are localized at one atom. (anion) |
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Term
| What is the relative strength of an ionic bond to a covalent bond and where do they exist? |
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Definition
Ionic bonds can be stronger than covalent bonds.
They exist between ions in solid state and in non-polar liquids. (Ex. hydrophobic alkane core in the membranes) |
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Term
| Why are the ionic bonds disrupted in water? |
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Definition
| The ionic bonds are disrupted in water because of (1) hydration of ions and (2) shielding of electrostatic interactions. |
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Term
| An electrostatic interaction has no ______. |
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Definition
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Term
| What is the Law describing the strength of electrostatic interactions and what does it mean? |
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Definition
| Coulomb's Law states that the strength of an electrostatic interaction is directly proportional to the magnitude of the charges involved. |
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Term
| _____ shields electrostatic interactions significantly, _____ much less effectively. |
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Definition
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Term
| How is an electrostatic interaction unique? |
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Definition
| An electrostatic interaction is the only interaction that can be both attractive and repulsive depending on the signs of the charges. |
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Term
| List an example of an electrostatic interaction. |
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Definition
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Term
| What is Coulomb's Law for 2 charges? Define the variables and units. |
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Definition
E = q1 x q2 / e x r
E = energy of interaction (erg)
q1 = charge 1 (esu)
q2 = charge 2 (esu)
e = dielectric constant (no units)
r = distance between charges (cm) |
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Term
| What is the dielectric constant also known as? What is it? |
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Definition
| The dielectric constant is also know as the permittivity. It characterizes the ability of the medium to shield the interactions among charges. Expressed as the relative value in comparison to a vacuum. |
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Term
| What is a charge-transfer reaction? |
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Definition
| A charge-transfer reaction results from a transfer of an electron between 2 molecules. |
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Term
| What are the qualities of the electron donor in a charge-transfer complex? The electron acceptor? |
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Definition
| The electron donor must have a low ionization potential. The electron acceptor must have high electron affinity. |
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Term
| Describe the strength of a charge-transfer complex in relation to a covalent bond. How is a charge-transfer complex easily monitored experimentally? |
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Definition
| A CT complex is much weaker than a covalent bond. It is easily monitored via the new band in the UV VIS spectrum. |
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Term
| List two examples of a charge-transfer complex. |
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Definition
Electron deficient and electron rich aromatic rings.
Melanin (eye pigment) and certain drugs with aromatic rings. |
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Term
| How is the dipole moment defined? What is the symbol and units? |
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Definition
The dipole moment (mu) is defined using the partial charges (delta) at the centers of positive and negative charges int he molecule and the distance (d) between the centers.
mu = delta x d
= esu x cm |
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Term
| What is the dipole moment of symmetric molecules? |
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Definition
| 0 (no distance between center of charges x charge is still 0) |
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Term
| What is a permanent dipole? |
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Definition
| Permanent charges in molecule that lead to an electrostatic interaction (Keesom). |
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Term
| What is an induced dipole? |
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Definition
| When the molecule gets in the vicinity of a charged molecule (or in an electric field), the electron cloud is deformed (polarized) and a new dipole originates - leads to induced (Debye) electrostatic interaction. |
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Term
| What is an immediate dipole? |
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Definition
| Due to fluctuation of electrons, gives rise to dispersion (London) interaction. |
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Term
Ion - Permanent Dipole Interaction
Coulomb's Law Equation |
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Definition
E = (q x d x delta) / (e x r^2)
E = energy of interaction
q = charge of ion
d = distance between partial charges, delta
delta = partial charge
e = dielectric constant
r = distance between ion and center of partial charges |
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Term
| What is the polarizability of a molecule and what is its symbol? What is it the proportionality constant between? |
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Definition
The polarizability (alpha) of a molecule is its tendency to have the electron cloud deformed in an electric field. It is also the proportionality constant between the induced dipole (mu-i) and the electric field (E).
induced dipole (mu-i) = alpha (polarizability) x E (electric field) |
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Term
| What is the relationship between polarizability of a molecule and its size? Why? |
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Definition
| Larger molecules have a larger alpha than smaller molecules because because their electrons are more distant from the nuclei and are easier to attract or repulse. |
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Term
| What are dispersion interactions also called? Where are they found? |
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Definition
| Dispersion interactions are sometimes called a London interaction. They are ubiquitous, meaning they are found in every interaction, even if the interaction partners don't have partial charges. |
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Term
| What is the cause of a dispersion interaction? |
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Definition
| Short-term electrostatic interaction causes charges to originate due to mobility of electrons and polarizability of electron clouds. |
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Term
| What is an example of a dispersion interaction? |
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Definition
| Carbon atoms of drugs with acyl chains of phospholipids in membrane core. |
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Term
| How is a hydrogen bond formed? |
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Definition
| It is formed between an electron-deficient hydrogen and an electron rich atom (N, O, S, etc.). An electron-deficient hydrogen is a hydrogen covalently bound to an electronegative atom. |
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Term
| Hydrogen bonds have ______ directionality. |
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Definition
| Limited -- more than just an electrostatic interaction! |
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Term
| List some examples of Hydrogen bonds. |
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Definition
Ex: NH2, OH groups with water molecules COO- with NH2 groups
It is a hydrogen bond if 3 atoms make a line, +/- 20 degrees. Otherwise it is just an electrostatic interaction. |
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Term
| List 6 weak interactions and their relative energy (kJ/mol). |
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Definition
Ion - Dipole: 20-40
H bond: 10-40
Dipole - Dipole (Keesom): 5-25
Ion-induced Dipole: 3-15
DIpole-induced Dipole (Debye):2-10
Dispersion (London): 0.05 - 40 |
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Term
| What is a hydrophobic interaction? What does it cause? |
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Definition
An indirect interaction caused by thermodynamically unfavorable formation of hydration layers on the non-polar molecules.
It causes association of non-polar molecules in aqueous media. |
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Term
| What are the 3 driving forces for a hydrophobic interaction? |
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Definition
(1) Self-assembly of phospholipid bilayers.
(2) Packing globular proteins.
(3) Binding of drug molecules to receptors and other macromolecules. |
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Term
| What is the cause of short-range repulsion and where does it occur? |
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Definition
| Short-range repulsion is caused by repulsions of electron clouds at short distances and it is ubiquitous. |
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Term
| Answer the following question for both strong and weak interactions: What is the structure of the molecule in the interaction vs. its original form? What is its relative activation energy? How fast does the interaction form? |
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Definition
Weak - Same, Low, Fast
Strong - Different, High, Slow |
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Term
| What processes do only weak interactions participate in? |
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Definition
| Finish within seconds or less in a homogenous solution. |
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Term
| What are H-bond acceptors? What are H-bond donors? |
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Definition
| Heteroatoms (O, N, S, P, ...) are H-bond acceptors. Hydrogens bound to heteroatoms are H-bond donors. |
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