MCAT Organic Chemistry (Princeton Review) QUESTIONS AND ANSWERS| GRADED A

MCAT Organic Chemistry (Princeton Review) Saturated Correct Answer: -Max number of H atoms attached -Single bonds Saturation Equation Correct Answer: CnH2n+2 Unsaturated Correct Answer: -Double bonds, triple bonds, ring structures Degrees of Unsaturation (DOU) Correct Answer: -DOU = sum of π bonds and rings -1 DOU = 1 π bond or ring Unstable Molecules Correct Answer: -High energy -Reactive with their environment -Shorter lifetimes Stable Molecules Correct Answer: -Low energy -Less reactive with their environment -Longer lifetimes Ideal Bond Angles Correct Answer: 109.5 Ring Strain Correct Answer: -Bond angles 109.5 -Destabilizes ring -Weakens C-C bonds -Increase reactivity Electronegative Substituents Correct Answer: -Withdraw electron density (oxygen, halogens) Electropositive Substituents Correct Answer: -Donate electron density (alkyl groups) Resonance Stability Correct Answer: -Occurs due to the delocalization of electrons -pos/neg charge or lone pair e- adjacent to π bond Bronsted-Lowry Acids Correct Answer: -Donate H+ and leave behind conjugate base -More stable base = more acidic conjugate acid 4 Factors that affect acid strength by altering conjugate base stability Correct Answer: 1.) Electronegativity 2.) Resonance 3.) Induction Nucleophiles (Nu-) Correct Answer: -Nucleus loving -Electron rich -Full or partial neg. charge -Donates pair of electrons and forms covalent bond -Lewis base -Nucleophile "attacks" electrophile Lewis Base Correct Answer: Donates pair of electrons Nucleophile Trends Correct Answer: 1.) Charge: negative charge makes stronger nucleophile 2.) Electronegativity: nucleophilicity increases as electronegativity decreases 3.) Size: nucleophilicity increases as size increases Nucleophilicity Trends Correct Answer: -Increase right to left across row -Increase down a group Basicity Trends Correct Answer: -Increase right to left across a row -Increase up a group Electrophiles Correct Answer: -Electron loving -Electron deficient -Full or partial positive charge -Accepts a pair of electrons -Lewis acid Lewis Acid Correct Answer: Accepts pair of electrons Good Leaving Group Trends Correct Answer: -Stable in solution -Resonance stabilizes charge -Weak base (Cl- Br- I-) -Neutral leaving groups are more stable than charged leaving groups Bad Leaving Group Trends Correct Answer: -Unstable in solution, usually due to their charge -Strong bases (HO-, RO-, NH2-) -Acid catalysis (protonation) can make a bad leaving group good -Hydrogens or alkanes never leaving groups Isomers Correct Answer: Different compounds with the same molecular formula Structural (Constitutional) Isomers Correct Answer: -Different atomic connectivity -Different chemical/physical properties Conformational Isomers Correct Answer: -Same atomic connectivity -Differ by rotation about 1 or more σ bonds -Identical chemical/physical properties -Cannot be isolated Cyclohexane Most Stable Conformation Correct Answer: -Chair -More stable to have larger groups in equatorial position (minimizes steric interactions) Chirality Correct Answer: -Not superimposable mirror images -No plane of symmetry Chiral Centers Correct Answer: -sp3 hybridized -Tetrahedral geometry -Four different substituents Calculating Number of Possible Isomers Correct Answer: 2^n -n = # of chiral centers Dextrorotatory (d) Correct Answer: (+) = clockwise rotation Levorotatory (l) Correct Answer: (-) = counter-clockwise rotation Optically Active Correct Answer: -Can rotate plane-polarized light -d or l -Physical property that cannot be predicted by structure and must be measured with polarimeter Absolute Configuration (R or S) Correct Answer: -R = clockwise rotation -S = counter-clockwise rotation Stereoisomers Correct Answer: -Same atomic connectivity -Differ in spacial arrangement of substituents Enantiomers Correct Answer: -Non-superimposable mirror images -Each has the opposite configuration at ALL chiral centers Diastereomers Correct Answer: -Non-superimposable, non-mirror images -Opposite configuration for at least one but not all chiral centers Geometric Isomers Correct Answer: -Subset of diastereomers -Restricted in rotation about a double bond or ring -Do not require chiral centers -All chemical/physical properties are different -cis and trans