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Orgo 1 (OAT)
| Question | Answer |
|---|---|
| What is a molecular formula? | Shows the number of atoms of each element in a compound (e.g., pentane = C₅H₁₂). Does not distinguish structural isomers. |
| What is a condensed formula? | Identifies the specific structural isomer by specifying the order of atom attachment (e.g., CH₃CH₂CH₂CH₂CH₃). |
| What does bond-line (skeletal) notation represent? | Each vertex = a carbon atom; hydrogens bonded to carbon are implied. More accurately depicts molecular geometry. |
| What do wedge bonds vs. dashed bonds represent? | Wedge = atom coming out of the page (toward viewer). Dashed = atom going into the page (away from viewer). |
| What are constitutional (structural) isomers? | Compounds with the same molecular formula but different connectivity of atoms. |
| How many structural isomers does C₆H₁₄ have? | 5 structural isomers. |
| What is an electron domain? | A lone pair or a bond on an atom. |
| What is the steric number? | The total number of electron domains on an atom. |
| What hybridization corresponds to steric number 4, 3, and 2? | 4 → sp³ | 3 → sp² | 2 → sp |
| What is the % s and % p character of sp³, sp², and sp orbitals? | sp³: 25% s, 75% p | sp²: 33% s, 66% p | sp: 50% s, 50% p |
| Do cations or radicals contribute to the electron domain count? | No. Cations have an empty unhybridized p orbital; radicals have a single unpaired electron in an unhybridized p orbital. Neither counts as an electron domain. |
| What is a sigma (σ) bond? | Formed by direct (head-on) overlap of 's' orbitals and/or hybrid AOs. |
| What is a pi (π) bond? | Formed by lateral (side-by-side) overlap of unhybridized 'p' orbitals. |
| How many σ and π bonds are in single, double, and triple bonds? | Single: 1σ | Double: 1σ + 1π | Triple: 1σ + 2π |
| What is the molecular geometry, bond angle, and hybridization of a carbon with 4 bonds, 0 lone pairs? | Tetrahedral, 109.5°, sp³ |
| What is the molecular geometry of sp³ with 3 bonds, 1 lone pair? | Trigonal pyramidal, <109.5° |
| What is the molecular geometry of sp³ with 2 bonds, 2 lone pairs? | Bent, <109.5° |
| What is the molecular geometry of sp² with 3 bonds, 0 lone pairs? | Trigonal planar, 120° |
| What is the molecular geometry of sp² with 2 bonds, 1 lone pair? | Bent, <120° |
| What is the molecular geometry of sp with 2 bonds, 0 lone pairs? | Linear, 180° |
| What three rules must each resonance structure obey? | 1) Same atomic skeleton (no atom movement) 2) Valid Lewis structure 3) Same net charge |
| What are the four rules for determining the most significant resonance contributor? | 1) Maximize complete octets 2) Minimize formal charges 3) Negative charge on more electronegative atom is more stable 4) Positive charge on less electronegative atom is more stable |
| What is the resonance hybrid? | An average of all resonance structures; indicates areas of high and low electron density. Resonance structures are NOT separate molecules. |
| How does resonance affect hybridization? | If a lone pair is delocalized through resonance, it does not count as an electron domain — the atom becomes sp² instead of sp³. |
| What is a Brønsted-Lowry acid and base? | Acid = proton (H⁺) donor. Base = proton (H⁺) acceptor. Reaction produces a conjugate base and conjugate acid. |
| What is a Lewis acid and base? | Lewis acid = electron pair acceptor. Lewis base = electron pair donor. They form a Lewis acid-base adduct. |
| What is Ka and what does a high Ka indicate? | Ka = [H₃O⁺][A⁻]/[HA]. High Ka = strong acid (extensive dissociation). |
| What is the relationship between Ka and pKa? | Inversely related. Stronger acid → higher Ka → lower pKa. Weaker acid → lower Ka → higher pKa. |
| What does a compound's pKa measure? | The stability of the compound's conjugate base. More stable conjugate base → lower pKa → stronger acid. |
| When do acids and bases become deprotonated? | When pH > pKa. |
| Which side do acid-base reactions favor? | Formation of the weaker acid (higher pKa). |
| What is the CARDIO acronym for ranking acidity? | Charge, Atom, Resonance Delocalization, Induction, Orbital hybridization |
| CARDIO — Charge: How does charge affect acidity? | Acidity increases with increasing positive charge. H₃O⁺ > H₂O > OH⁻ (decreasing pKa, increasing acidity) |
| CARDIO — Atom: How does position on the periodic table affect acidity? | Acidity increases going DOWN a column (larger atomic radius stabilizes conjugate base) and LEFT to RIGHT across a row (increasing electronegativity). |
| CARDIO — Resonance: How does resonance affect acidity? | Greater resonance delocalization of conjugate base negative charge → more stable conjugate base → stronger acid. (e.g., acetic acid more acidic than ethanol) |
| CARDIO — Induction: How do electronegative substituents affect acidity? | Electronegative atoms on nearby carbons pull electron density away from the conjugate base, stabilizing it → increases acidity. More electronegative groups = stronger inductive effect = stronger acid. |
| CARDIO — Orbital Hybridization: How does hybridization affect acidity? | Greater s-character → negative charge held closer to nucleus → more stable conjugate base → stronger acid. sp (50% s) > sp² (33% s) > sp³ (25% s). |
| What are the four intermolecular forces (IMFs) ranked weakest to strongest? | London Dispersion Forces (LDF) < Dipole-Dipole < Hydrogen Bonding < Ion-Ion interactions |
| What are London Dispersion Forces (LDF)? | Weakest IMF; present in ALL molecules; only IMF in nonpolar molecules. Arise from momentary (instantaneous) dipoles inducing opposite dipoles in neighboring molecules. |
| What are dipole-dipole interactions? | Occur between polar molecules. Partial positive end of one molecule attracts partial negative end of another. LDF + dipole-dipole = Van der Waals forces. |
| What is hydrogen bonding? | Especially strong dipole-dipole interaction occurring when F, O, or N is directly bonded to H. (N–H, O–H, F–H bonds are highly polarized.) |
| Rule about hydrogen bonding | Hydrogen bonds are weak against covalent and ionic (intramolecular) bonds, but stronger than most dipole-dipole (intermolecular) interactions. |
| What are ion-ion interactions? | Occur between cations and anions; the strongest IMF. |
| What is "like dissolves like"? | Compounds dissolve best in solvents that participate in the same intermolecular forces (e.g., nonpolar solutes in nonpolar solvents) |
| How does hydrocarbon chain length affect water solubility? | Longer hydrocarbon chains = more nonpolar/hydrophobic character = less soluble in water. |
| How does branching affect boiling point? | Increased branching → decreased boiling point (less surface area → weaker LDF interactions). Straight-chain isomers have higher boiling points. |
| How does branching affect melting point? | Generally, increased branching decreases melting point. However, high molecular symmetry increases melting point (allows tighter crystal packing). |
| What determines melting and boiling points? | Strength of intermolecular forces. Stronger IMF → higher MP and BP. Larger molecules (more surface area) → stronger LDF → higher MP/BP. |
| What is an arrow-pushing mechanism? | A way to depict electron flow as bonds are broken and formed during a reaction. Arrows show movement of electrons, not atoms. |
| What does a double-headed curved arrow mean in a mechanism? | Movement of an electron pair (two electrons). |
| What does a single-headed (fishhook) arrow mean in a mechanism? | Movement of a single electron (seen in radical reactions, typically in pairs). |
| What does a bond-originating arrow indicate? | Movement of electrons from a bond (σ or π bond breakage); electrons move to form a new bond or become a lone pair/radical on an adjacent atom. |
| What does an atom-originating arrow indicate? | The atom has a lone pair or is a radical; the arrow shows those electrons moving to form a new bond with another atom. |
| What is conserved during arrow-pushing mechanisms? | Overall charge. Individual atom charges may change, but the total charge of the system stays the same. |
| What is Kb? | The base dissociation constant. Measures how extensively a base dissociates in water. Kb = [BH⁺][OH⁻]/[B] |
| What is the relationship between Kb and pKb? | Inversely related. Stronger base → higher Kb → lower pKb. Weaker base → lower Kb → higher pKb. |
| How does Kb/pKb parallel Ka/pKa? | Exactly the same logic — just applied to bases instead of acids. Strong base = high Kb = low pKb. Weak base = low Kb = high pKb. |
| What is the relationship between pKa and pKb of a conjugate acid-base pair? | pKa + pKb = 14 (at 25°C). The stronger the acid, the weaker its conjugate base, and vice versa. |
| If a base has a very high pKb, what does that tell you? | It is a weak base — it does not dissociate extensively and has a relatively unstable conjugate acid. |
| What is the general rule for which side an acid-base equilibrium favors? | Equilibrium favors formation of the weaker acid — the side with the higher pKa. |
| In an acid-base reaction, if the reactant acid has pKa = 10 and the product acid has pKa = 14, which side is favored? | The product side — because the product acid (pKa = 14) is the weaker acid (higher pKa). |
| Why do strong bases favor the product side in equilibrium? | Strong bases are highly reactive and produce a weak (stable) conjugate acid. The weaker conjugate acid on the product side drives equilibrium forward. |
| At what condition do both acids and bases become deprotonated? | When pH > pKa of the compound. |
| Why do acids undergo deprotonation at a relatively low pH? | Acids have a stable conjugate base and a low pKa, so the threshold pH needed to deprotonate them is reached more easily. |
| Why do bases undergo deprotonation only at very high pH (or not at all)? | Bases have an unstable conjugate base and a high pKa, so an extremely high pH is required to deprotonate them. |
| When do two resonance structures NOT contribute equally? | When they are not equivalent in energy (e.g., different numbers of formal charges or octets). The more stable structure contributes more to the hybrid. |
| Comparing methanol, ethanol, and propanol — which is most soluble in water and why? | Methanol — it has the shortest (smallest) hydrocarbon chain, so the hydrophobic region is smallest and the OH group dominates, allowing maximum hydrogen bonding with water. |
| What IMF must a solute and solvent share for the solute to dissolve well? | They must be capable of the same type (or compatible types) of intermolecular forces. A mismatch in IMF type leads to poor solubility. |
| How many resonance structures do nitro groups have | 2 |
| How many resonance structures does a benzylic compound have | 5 |
Created by:
smurtab