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27 Cards in this Set
- Front
- Back
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What effect does branching have on IMF and why?
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Decreases SA of molecule, thus decreasing IMF (VDW)
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Effect of increasing chain length on bp, mp, and density?
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INCREASE
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Effect of increasing branching on bp, mp, and density?
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DECREASE
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List stability of radicals by classification of carbons.
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tert>second>primary>met
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What carbon type does radical bromination prefer? Why?
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Tertiary, bromination is slow, likes most stable free radical
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What carbon type does radical chlorination prefer? Why?
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primary because of ABUNDANCE; it's faster, usually get mixed products
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General equation for combustion
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Alkane + O2-->CO2+H2O+heat
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Why is pyrolysis?
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AKA CRACKING; heat used to break down molecules to smaller-chain alkyl radicals, which recombine to form a variety of alkanes.
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How is nucleophile strength determined? Provide a list of nucleophiles in order of nucleophilicity.
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Base strength
OR->OH->RCO2->ROH>H2O |
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In protic solvents, how is nucleophile strength determined? Why? Provide a list of nucleophiles in order of nucleophilicity in protic solvents.
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Size because larger molecules can shed solvent molecules.
CN->I->OR->OH->Br->Cl->F->H2O |
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In aprotic solvents, how is nucleophile strength determined? Why? Provide a list of nucleophiles in order of nucleophilicity in aprotic solvents.
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Basicity: molecules are naked (not solvated)
F->Cl->Br->I- |
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How is leaving group strength determined? Provide a list of leaving groups in order of strength.
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Weak bases = good LGs; I->Br->Cl->F-
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What types of solvent and carbon type stabilize SN1 reactions? Why?
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Polar w/lone pair e-'s to donate (H2O, Acetone) to stabilize C+; same with charge declocalization: Tert>Sec>Prim>Met
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What is the rate of SN1 reactions determined by?
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[original molecule]
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How can the rate of SN1 reactions be increased?
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By doing anything that stabilizes/accelerates C+ formn:
1) Highly subst'd haloalkanes 2) Highly polar solvents (polar protic = ideal) to stabilize interm. state 3) Weak bases as LG (GOOD LG) |
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What is the rate of SN2 reactions dependent on?
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[substrate] & [Nuc]
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How can the rate of SN2 reactions be increased?
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Increase conc of substrate and nuc
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What is the difference between an intermediate and transition state?
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Inter = well-defined species w/finite lifetime
TS = theoretical structure used to explain mech |
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How does SN1 stereochemistry differ from that of SN2?
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SN1: involve C+ which are planar and achiral, so if original cmps is optically active, racemic mixture produced (opt inact)
SN2: TS is chiral since nuc attacks from one side of C and LG leaves from other, molecules flips, resulting in inversion of configurn |
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For SN1 & SN2 reactions list:
Number of steps Solvent preferred Carbon type preferred Rate equation Stereochemistry of products |
2; 1
polar protic; polar aprotic tert>2>1>met; opp K[RX]; K[RX][Nu] racemic; opt act or inact prods |
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Compare melting points of trans alkenes with that of cis alkenes.
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Greater b/c better packers in solid state due to symmetry
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How does polarity differ between symmetric trans and cis alkenes? How does this affect boiling points?
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Trans: non-polar due to cancellation of dipoles
Cis: Polar Cis have greater bps due to polarity |
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What are favorable conds for E1 reactions?
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Highly polar solvents, highly branced C chains, good LG, weak nucs in low []; competes w/SN1, but can win out with high heat
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What are favorable conds for E1 reactions?
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Strong base, halide ion ANTI to proton leaving
Steric hinderance has no effect, so branching won't do anything but Strong bases favor E2 over SN2 (SN2 wants strong nucs) |
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Describe usefulness of H2, Pd/C
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Syn addition of H's to alkenes (REDUCTION)
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What is Markovnikov's rule?
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Add'n of something to most subst'd C in double bond
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Compare the boiling point of an internal alkyne with that of a terminal alkyne.
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Interal is higher (more stable)
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