Organic Chemistry - Final Exam

Organic Chemistry - Final Exam Name the 6 polar aprotic solvents - acetone, acetonitrile, DMSO, DMF, HMPA, THF Name the 5 polar protic solvents - acetic acid, ethanol, formic acid, methanol, water ______ and ______ mechanisms are two step reactions that have _____ intermediates. - SN1; E1; 2 Intermediates each ______ and ______ mechanisms are one step reactions that have _____ intermediates. - SN2; E2; 1 Intermediate each Allylic - resonance stabilized (carbon bonded directly to a C=C) ______ always proceeds with a backside attack, causing an inversion of configuration at the stereogenic center. The _______ and _______ group are 180° from each other. - SN2; Nucleophile; leaving group During an SN2 reaction, what happens during the backside attack of a ring? - Converts starting material with a cis group to being trans What is the process to determining which product of a (beta) elimination reaction is the major/minor? - First apply the Zaitsev rule (the major product has the more substituted double bond); If a mixture of stereoisomers is possible, the major product is the more stable stereoisomer. Reaction Check List - SN1: ∧Nucl, ∨Base - 3°, Protic (not 1°) SN2: ∧Nucl, ∨Base - 1°, Aprotic, (not 3°) E1: Bulky/Nonnucl. Base - 3°, ∨Base, Protic, (not 1°) E2: Bulky/Nonnucl. Base - 3°, ∧Base, Aprotic, (not 1°) When determining the more stable stereoisomer (to find the major product), what are 4 possible areas to look at? - 1) If E2: Have to be anti-periplanar 2) If E1: Determine the more stable carbocation by higher R substitution 3) Alkene more stable when more R groups 4) Trans Cis Alkyne Synthesis is done with what type of reaction mechanism? How? - E2; two successive dehydrohalogenation (E2) reactions What ways can you gather enough information to rank substances by basicity? - 1) strongest acid → weakest (conj.) base 2) As pKa of H-A gets smaller, the basicity of -A: increases 3) As Ka of H-A gets larger, the weaker the -A: Definition of Lewis Acid - electron pair acceptor; any e- deficient species that is capable of accepting an e- pair is a Lewis Acid; any molecule or ionic species that can form new covalent bond by accepting an e- pair; all BL acids are Lewis acids, but reverse is not necessarily true Definition of Lewis Base - electron pair donor; structurally same as BL base (both have e- pair); unlike BL base, Lewis can donate pair to anything electron deficient; any molecule or ionic species that can form a new covalent bond by donating an e- pair. Definition of B-L Acid. What requirements must they have? Give its symbol. - a proton donor; must contain hydrogen; H-A Definition of B-L Base. What requirements must they have? Give its symbol. - A proton acceptor; must contain available e- pair (LP or π); B: Any reaction in qhich one species donates an electron pair to another species is a _____________. - Lewis Acid-Base Reaction What is the rule to being able to determine if a base is strong enough to deprotonate (ionize) a given acid? - an acid can be deprotonated by the conjugate base of any acid having a higher pKa (pKa of equal value will not cause deprotonation) Which has properties to be more acidic than the other between: Br & S (EN, size, etc.) - Br has higher EN and is more acidic if compared to similar molecule with S Which has properties to be more acidic than the other between: O & Cl (EN, size, etc.) - O has higher EN and is more acidic if compared to similar molecule with Cl How to determine which hydrogen is most acidic... - look at all elements bonded to H within that molecule. Whichever hydrogen is connected to the one with the highest EN will be the one that is most acidic. When is the only time size matters and needs to be taken into account? - When the specific atom being looked at is directly bonded to the acidic hydrogen What 2 things to be careful on when working LB Acid-Base Rxns with possible inductive effects... - Size does not matter, because electron withdrawing 'group' is not directly connected to the acidic hydrogen. ONLY WORRY LOOK AT ELECTRONEGATIVITY! EN of withdrawing group can only carry up to 5 bonds. When looking at resonance effect, make sure to remember do what? - only draw resonance structures for the conjugate bases! What is the definition and formula for equilibrium constant? - Expression which relates amount of starting material and product at equilibrium; Keq=[-A:][BH]/[HA][B:] {prod./reactants) What is the definition and formula for the acid ionization constant? - Value that represents the strength of an acid (H-A); Ka=[-A:][BH]/HA (Ka=Keq[H2O]) ... doesn't include water What is the formula for pKa? - pKa=-LOG[Ka] What are the factors that determine acid strength? - 1) Size of (-) if in same column; 2) EN of (-) if in same period; 3) Inductive effects of EN atom not touching the acidic hydrogen; 4) Resonance effects - compare conj. bases resonance; 5) Hybridization effects of A (H-A)