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30 Cards in this Set
- Front
- Back
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What are aufbau, Pauli exclusion, and Hunds?
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aufpau: lowest energy orbital fills up first
pauli exclusion: two orientations with opposite spin, also has concept of hybridization hunds: one electron occupies each orbital with spins parallel in all orbitals until half-full |
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What is an example of a coordinate covalent bond?
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Boronhydride ammonia complex
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What are sigma and pi bonds?
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sigma
-overlap of 2 s, 1 P 1 S, or 2 P orbitals -lower in energy -less reactive -rotation possible pi: -sideway or parallel overlap of unhybridized p -electrons loosely held -higher in energy -more reactive -rotation not possible |
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What are some polar and nonpolar molecules?
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polar:
-water, methanol, ammonia nonpolar: -carbon dioxide, mathane, ethane, benzene |
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What are the rules for resonance structures?
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used to determine formal charges
1. individual resonance forms are imaginary 2. resonance forms differ only in placement of pi or nonbonding electrons 3. different resonance forms of a substrate don't have to be equivalent (ex. Acetyl CoA) 4. resonance forms obey normal rules of valency 5. The resonance hybrid is more stable than any individual resonance form |
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What are some important organic acids and bases?
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Carboxylic Acid - Glutamate: pKa = 2-5
Imidazole - Histidine: pKa = 7 (impt in biochemistry because pKa is close to neutral) Thiol - Cysteine: pKa = 8-9 Amine - Lysine: same as Cysteine Phenol - Tyrosine: pKa = 9-10 Guanidine - arginine: pKa = 12.5 |
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What are qualities of bronsted and lewis acids and bases?
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Bronsted focuses on protons, Lewis focuses on electrons
All bronsted acids and bases are lewis acids and bases ex of Lewis: Boron Trifluoride (lewis acid) bonding with Dimethyl Ether (Lewis Base) Magnesium is an example of a biologically active Lewis Acid (used in ATP) Lewis base is a nucleophile |
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What are the functional groups with electronegative atoms?
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alkyl halides
alcohols ethers alkyl phosphates thiols sulfides disulfides |
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What functional groups have a carbonyl group?
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aldehyde
ketone carboxylic acid ester thioester amide acid chloride (most active becuase of high electronegative nature of choloride) |
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What are properties of Alkanes?
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known as paraffins (meaning little affinity)
react with oxygen, halogens, and few others reaction with oxygen: occurs during combustion in an engine, alkane is used as fuel ONLY REACT UNDER EXTREME CONDTIONS |
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What is torsional strain?
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strain molecule has that is caused by interaction between C-H bonding orbitals of one carbon with antibonding orbitals on adjacent carbon
also known as eclipsing strain accounts for extra 12 kJ/mol of energy in eclipsed conformation of ethane |
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What is the Gauche conformation?
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higher energy than anti conformation
has 3.8 kJ/mol of steric strain steric strain: -repulsive interaction when two groups are closer than their atomic radii allow |
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What are the 3 kinds of ring strain?
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1. Angle strain: dude to bond angles
2. Torsional strain: due to eclipsing of bonds 3. Steric Strain: when atoms approach each other too closely |
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What are characteristics of cyclopropane, cyclobutane, cyclopentane, and cyclohexane?
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Cyclopropane:
-most strained of all rings -angle strain: caused by 60 degree C-C-C -torsional strain: eclipsed C-H bonds on neighboring C atoms Cyclobutane: -angle strain: less than cyclopropane -torsional strain: more than cyclopropane due to larger number of ring hydrogens cyclopentane: -angle strain: very minimal -torsional strain: large amount -less strain than both others -puckered formation Cyclohexane: -strain free, chair conformation -all angles near 109 -C-H bonds staggered |
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What are properties of the chair conformation of cyclohexane?
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only ONE form of a monosubstituted cyclohexane
exchanging axial and equatorial positions = ring flip |
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What causes the energy difference between axial and equatorial conformations?
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steric strain caused by 1,3 diaxial interactions
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What is common between methylcyclohexane and gauche butane?
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identical steric strian when methylcyclohexane has hydrogen atoms in the axial position
methylcyclohexane is more stable in the equatorial |
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What is the preferred arrangement for a disubstituted cyclohexane?
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trans and equatorial
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What is Decalin?
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exists in cis or trans (more stable)
cis and trans are not interconvertible by ring-flip or other rotations |
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What are examples of addition, elimination, substitution reactions, and rearrangement reactions?
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Addition:
-fumarate with water to yield malate Elimination: -hydroxybutyryl ACP to yield trans-crotonyl ACP and water Substitution: -ester such as methyl acetate with water to yield a carboxylic acid and alcohol Rearrangement: -dihydroxyacetone phosphate --> glyceraldehyde 3-phosphate |
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What are the two ways that a covalent bond can break?
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1. symmetrical - homolytic
-one electron remains with each product fragment 2. unsymmetrical - heterolytic -both bonding electrons remain with one product fragment, leaving the other with a vacant orbital |
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What are mechanisms of Radical and Polar reactions?
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Radical:
-involves symmetrical bond breaking and making -free radical reactions Polar: -involves unsymmetrical bond breaking and making -species that have even number of electrons |
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What are characteristics of Radical reactions?
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1. Radical substitution reactions:
-sigma bonds 2. Radical addition reactions: -pi bonds Industrial radical reaction: -chlorination of methane to yield chloromethane -substitution reaction steps: initiation, propagation, termination Biological radical reaction: -prostaglandin synthesis from arachidonic acid |
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What are characteristics of Polar reactions?
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Nucleophile:
-substance that is nucleus loving -either neutral or negatively charged -forms a bond by donating a pair of electrons to a positively polarized, electron-poor atom -negatively polarized electron-rich atom -LEWIS BASES, EX. RNH2 electrophile: -substance that is "electron-loving" -positively charged, electron poor -accepts electrons from a nucleophile -neutral or positively charged -LEWIS ACIDS, EX. BF3 example of Polar reaction: addition of H2O to Ethylene in presence of strong acid water becomes H3O (electrophile) |
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What are properties of Keq?
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Keq > 1: Product concentration much larger than reactant concentration
-reaction proceeds from left to right Keq = 1: equilibrium Keq < 1: Reactants more than products -reaction proceeds from right to left |
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What are properties of Gibbs Free energy?
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when G is negative:
-reaction is exergonic -favorable equilibrium constant ( Keq > 1) -occurs spontaneously When G is positive: -reaction is endergonic -unfavorable equilibrium constant ( Keq < 1) -not spontaneous G = -RTlinKeq or Keq = e^-G/RT G = H - TS |
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What are characteristics of change in Enthalpy?
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H = Hprod - Hreact
-difference in strength between bonds broken and bonds formed negative H: -exothermic -products more stable than reactants -products have less energy but stronger bonds than reactants positive H: -endothermic -products less stable than reactants -products have more energy but weaker bonds than reactants |
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What are characteristics of Entropy?
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S = Sprod - Sreact
-change in molecular disorder negative S: -disorder decreases ex. addition rxn: A+B --> C Positive S: -disorder increases ex. elimination rxn: A --> B + C |
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What are some important cyclic structures?
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Chrysanthemic acid: (3 membered rings)
-occurs naturally as esters Prostaglandins: (5 membered-rings) -potent hormones Steroids: (6 membered-rings) -tetracyclic lipids Beta Lactam: (4 membered ring) -found in penicllin |
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What is Baeyer's theory?
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assumed all cycloalkanes to be flat
angle strains only occur in small rings that have little flexibility angle strain: strain induced in a molecule when bond angle are forced to deviate from the ideal 109 degree tetrahedral value |
