midterm1
Quiz yourself by thinking what should be in
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Help!
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| Branched or unbranched hydrocarbons have higher boiling point? | Unbranched
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| What can you use to determine most acidic proton? | Electronegativity, and resonance
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| A hydrogen on the alpha position of a carbonyl is _____ acidic | weakly
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| In radical addition, what wont you see? | CH3 and Br on same cyclo carbon
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| ROOR is a tipoff that? | It's a radical
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| ROOR does not work with H - ____ | Cl
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| Alkanes show __ chemical affinity for other substances | little
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| Are alkanes often involved in chemistry of living organisms? | NO
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| During combustion, what are the products? | carbon dioxide, water
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| Does RXN of alkane with Cl2 occur? | Yes, when the mixture is irradiated with UV light
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| A standard Newman projection represents how many carbons? | 2
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| What causes the free rotation around the C-C bonds in ethane? | the sigma bond
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| gauche conformation causes what sort of strain? | steric
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| In methylcyclohexane, which conformation is more stable: the equatorial or axial? | equatorial
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| what is the cause of the steric strain on axial conformations of substituted cyclohexanes? | the axial methyl group on C1 is too close to the axial hydrogens 3 carbons away.
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| on an axial monosub'd cyclohexane, how many axial interactions with hydrogens would the substituent have? | 2; an axial interaction with the hydrogen on either side
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| in disubstituted cyclohexanes, is the equatorial position always more stable | no, need to analyze all steric interactions in the possible chair conformations before deciding which is favored
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| what is the common structure of steroids? | 3 six membered rings, 1 five membered ring fused together
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| which cycloalkane is strain-free? | cyclohexane, b/c it adopts puckered chair conformation
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| Which type of radicals do NOT form? | Phenyl
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| how do you determine stability of a carbocation? | stability increases from primary to tertiary
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| what is the hydration reaction? | water adds to alkenes to yield alcohols
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| in these acidic reactions, what do you look for? | the spot with most carbons attached
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| what is the first step with acidic hydration and alkene/ring? | it degrades the alkene to an alkane
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| whats second step with acidic hydration? | H2O comes to the rescue
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| in radical RXNS, what can be a terminating step? | when 2 radicals come together to form a stable product
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| in radical substitution: which is selective: chlorine or bromine? | bromine
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| in radical substitution: which position types WONT chlorine go after? | phenylic and vinylic
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| are metals more or less EN charged than a carbon? | less
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| if Keq is less than 1 ... | the RXN goes in the reverse direction, from right to left
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| what is Gibbs free energy change? | the E change that occurs during a chemical RXN
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| does Keq tell you the rate of RXN or how fast equilibrium is reached? | NO
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| how can you tell if radical substitution? | hv, single blonds, Cl/Br
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| how can you tell if radical addition? | ROOR, HBr, double bond
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| how can you tell if electrophilic addition? | no hv, no ROOR
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| if you break pi, sigma, sigma and have sigma, sigma sigma, exo/endothermic? | exothermic
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| when asked about acid/base stability, consider: | the 4/5 rules, and whether tertiary, primary, etc.
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| whats the mnemonic for electrophilic addition? | most, basic, rescue. you add HBr across the double bond
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| when delta G is positive, Keq is ... | negative
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| when delta G is negative, which side preferred? | right side
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| what is the gauche value between CH3 and Br on Newman projection? | 0.3
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| What is the gauche value between Ch3 and CH3 on Newman projection? | 0.9
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| when you think of thermodynamic stability, think.... | internal double bonds more stable than external, and, the more carbons on it, the more stable.
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| if multiple carbocations could form...which one do you choose? | the more stable one, based on the ranking 3>2>1..
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| why is it that usually the first carbocation intermediate is a slow transition? | because it does not obey octet rule
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| break weak bonds, form strong bonds: ____thermic | exothermic
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| when determining sign of enthalpy, entropy, gibbs free energy: | delta H: use what type of bonds broken/formed
delta S: use randomness
delta G: use equation
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| how many transition states in electrophilic addition? | 2
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| what is "bromination"? | electrophilic addition with Br2
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| in one line, what happens with electrophilic addition? | you add ___ across the double bond
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| which electrons are relatively open to attack? | pi electrons in a pi orbital
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| Name a superbase: | LiCH3
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| Name some polar protic molecules: | H2O, D2O
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| another last way to evaluate side preferred: | can tell which is stronger acid/base by, which one more likely to donate protons..etc.
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| recap: how to tell which side preferred? | stability rules, stronger acid/base, the trend
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| least acidic protons are : | methylic
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| protic conatin which bonds? | O-H or N-H
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| all transition metal cations are Lewis ___ | acids. Al, B, Magnesium ion
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| when forming a standard carbocation, the formal charge will want to reside on the | most alkyl substituted side. (b/c more stable)
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| the energy profile goes down..due to: | progressive obeying of octet rule
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| what is LDA? | N with two isopropyls attached
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| Name 2 basic nucleophiles: | NaOH, LiNH2
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| Name 2 acidic non-nucleophiles: | H2SO4, H3PO4
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| CH3MgBr is a ___ | Superbase!
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| a strong acid has a stable ___ | conjugate base
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| external double bonds: more or less stable than internal? | less stable (more unstable)
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| greater alkyl substitution, the __ stable the double bond | more stable
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| all transition metal cations are: | Lewis acids
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| what does LDA do? | dehydrohalogenates
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| what else dehydrohalogenates? | NaNH2 with acetone
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