Chemistry Flashcards
What is Paramagnetism?
Electrons align with the magnetic fields and then return to orientation in absence of magnetic fields.
What is Diamagnetism?
Electrons resist alignment with magnetic field even in presence of an external magnetic field.
What is Ferromagnetism?
Electrons are strongly aligned even in absence of an external magnetic field.
What is the relationship between Keq and ∆G?
They are opposites within the same process. When Keq is greater than 1, then ∆G is less than 1 and this would be a spontaneous reaction. Vice Versa is to be assumed.
Arrhenius definition only works with…
Water! It can be applied only to reactions that occur in water because it defines acids and bases in terms of what happens when compounds dissolve in water.
What are the Arrhenius base and acid rules?
Arrhenius Acids are hydronium ion donors. Arrhenius Bases are hydronium ion acceptors. Hydronium is H3O+..
pH = ?
pH = -log (H+) or pOH = -log (OH-)
What is the relationship between Acids/Bases and their conjugates?
Strong acids make weaker conjugate bases. Weaker acids make stronger conjugate bases.
What are the Strong Acids to memorize?
HCl, HBr, HI, H2SO4 (sulfuric acid), HNO3 (nitric acid), HClO3 (chloric acid), HClO4 (perchloric acid)
What are the Weak Acids to memorize?
CH3COOH (acetic acid), H2CO3 (carbonic acid), HCN (hydrocyanic acid), HF, H3PO4 (phosphoric acid)
What are the Strong Bases to memorize?
NaOH, KOH, CsOH, Ca(OH)2, Ba(OH)2, Sr(OH)2, hydroxides made from group 1 (alkali) metals
What are the Weak Acids to memorize?
NH3 (ammonia), NH4OH (ammonium hydroxide), C5H5N (Pyridine)
What is the reduction potential?
Measured in volts and its energy per amount of charge. The tendency of a chemical to be reduced by gaining an electron. Higher electronegativity means higher reduction potential. Negative reduction potentials mean movement from positive side of battery to the negative.
AN OX
RED CAT
Electrons ALWAYS move from the anode to the cathode. The anode is oxidation and the cathode is reduction. Anions move toward the anode and cations move to the cathode.
Galvanic Cell
- Gets energy from spontaneous redox reactions
- Eₒ is positive
- ∆G is negative
- Cathode is (+)
- Anode is (-)
Electrolytic Cell
- Requires DC battery or AC source
- Eₒ is negative
- ∆G is positive
- Cathode is (-)
- Anode is (+)
Nucleophilic Addition
A nucleophile forms a sigma bond with an electron-deficient species. Can’t take place in the presence of excessive steric hinderance.
3 Steps:
1. Electrophilic carbonyl carbon bonds with nucleophile
2. Carbon-oxygen double bond is now broken, forming an alkoxide intermediate (oxygen has a negative charge).
3. Alkoxide gets protonated, making alcohol that is also attached to the nucleophile
Electrophile vs. Nucleophile
Electrophiles are lewis acids with positive charges. Nucleophiles are lewis bases with negative charges and they can use their electrons to make new bonds.
Aldehydes are better electrophiles than ketones.
What make the best Leaving Groups?
- Stable on its own
- Weakest bases and low energy
- Can take electrons and be stable with that negative charge or can spread out the negative charge
Examples: Water, alcohol, ethers, halides (the bigger the better), inorganic esters (H2PO4, HNO3), tosylates
Note: Anhydrides are good leaving groups as well
What makes the weakest Leaving Groups?
- Not stable
Example: hydroxides, alkoxides, carbanions, hydride (H-)
The relationship between pKa and acidity is…
pKa and acidity are inverse. As the pKa lowers, the acidity increases. The more positive the more acidic, the more negative the more basic.
What is the difference between polar protic and polar aprotic solvents?
Polar Protic: have protons and hydrogen bonding, the nucleophilicity of the halides increases down the table
Polar Aprotic: have no electrons to donate and no hydrogen bonding, the nucleophilicity of the halides increases up the table
Geminal and Vicinal Hack!
Gemini twins - Geminal
Same Vicinity - Vicinal
Aldol Condensation
When you add a base to a ketone, an enolate will be formed. Then, if you react this enolate with a ketone, it will become an aldol.
Enolates have a C=C bond with one of the carbons being bonded to an oxygen-carrying the negative charge.
Strong Oxidizing Agents are…
- KMnO4, Na2Cr2O7, Jones’ Reagent
- CrO3, H2SO4 in Acetone
H2CrO4
Makes Carboxylic Acids
Strong Reducing Agents are…
LiAlH4
Carboxylic Acid -> Primary Alcohol
Ketone -> Secondary Alcohol
Ester -> Alcohol
Amide -> Amine
Weak Oxidizing Agents are…
PCC
Converts primary alcohols to aldehydes, and secondary alcohols to ketones
Weak Reducing Agents are…
NaBH4
Converts aldehyde to primary alcohol and ketone to secondary alcohol.
Tollen’s Reagent
- Only oxidizes aldehydes to acids
- distinguish between aldehydes and ketones to identify reducing sugars
- Aldose give positive results (as well as terminal alpha-hydroxyketose)
- similar to Fehling’s and Benedict’s reagent
Tautomerization Note
Only happens where there is no alpha hydrogren.
Tautomerization begins when the partially negative electrons on the alcohol oxygen reach down to attack the sp2 (C=C) carbon atom
SN1 vs. SN2
SN1: polar protic solvents only, the most stable carbocation has the fastest rate due to the electron donating groups
SN2: polar aprotic solvents only, needs a strong nucleophile
SN1 involves one molecule while Sn2 involves two molecules.
Oxidation vs. Reduction Hack
Oxidation is gaining bonds to oxygen.
Reduction is gaining bonds to hydrogen.
Citric Acid Cycle Mnemonic
Can I Keep Selling Seashells for money, Officer?
Citrate - Isocitrate - Ketoglutarate - Succinyl CoA (allosteric inhibitor) - Succinate - Fumarate - Malate - Oxaloacetate
Weak Bases do not…
Weak Bases do not dissociate completely in water.
Relationship between atomic radii and ionization energy
As the atomic radii increases, ionization energy decreases
What is the difference between beta minus and beta plus decay?
Beta minus decay is electron emission where a neutron converts into a proton so the atomic # increases by one.
Beta plus decay is positron emission where a proton will become a neutron so the atomic # decreases by one.
Diamagnetic attracts or repels…
Diamagnetic weakly repels magnets and they are antiparallel to the magnetic field.
What is the purpose of contrast agents in MRIs?
Contrast agents increase MRI signals by increasing relaxivity of water molecules
How can you tell Disproportionation from Frost Diagram?
If above slope of two adjacent points on the line, it is likely to undergo disproportionation.
What is the reduction potential of voltaic/galvanic?
Positive! So that you should reverse the reaction to create a positive reduction potential and then add the reduction potentials together
How are glycosidic bonds formed?
The hydroxyl oxygen attacks the anomeric carbon of the hemiacetal forming the acetaal
How many hydrogen bonds are between each of the nitrogenous base pair?
A-T have 2 hydrogen bonds and G-C have hydrogen bonds.
What is the relationship between respiratory rate and blood CO2?
A lower respiratory rate means a higher blood CO2 and a higher H+ and carbonic acid.
Relationship between Electronegativity and Nucleophilicity
As the proposed atoms get more electronegative, the nucleophilicity increases.
To Find Binding affinity of a substrate for its ligand…
Kd = [S][L]/[S-L]
What can you read from reduction potentials?
A positive reduction potential means that the reaction was reduced when paired with hydrogen. A negative reduction potential means that the reaction was oxidized when paired with hydrogen.
Whichever one has the higher reduction potential is reduced and the other is oxidized.
In a Spontaneous reaction, E cell is…
Positive!
Also the species that gets reduced had the large reduction potential and the species that is oxidized has the smaller reduction potential.
Ecell = larger reduction potential - smaller reduction potential
In a nonspontaneous reaction, E cell is…
Negative!
Also, the oxidized species has a larger reduction potential and the reduced species has a smaller reduction potential.
Ecell = smaller reduction potential - larger reduction potential
If you see a voltmeter as a diagram,
You are most likely looking at a galvanic cell.
Current flowing cathode to anode, electrons flowing anode to cathode.
In a galvanic/voltaic cell, the cathode is the site of…
reduction!
KD and Binding affinity have an …. relationship
Dissociation constant is small so the binding affinity is large.
Amphipathic helices have hydrophobic residues every…
3 to 4 residues!
