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OChem Midterm


Branched or unbranched hydrocarbons have higher boiling point? Unbranched
What can you use to determine most acidic proton? Electronegativity, and resonance
A hydrogen on the alpha position of a carbonyl is _____ acidic weakly
In radical addition, what wont you see? CH3 and Br on same cyclo carbon
ROOR is a tipoff that? It's a radical
ROOR does not work with H - ____ Cl
Alkanes show __ chemical affinity for other substances little
Are alkanes often involved in chemistry of living organisms? NO
During combustion, what are the products? carbon dioxide, water
Does RXN of alkane with Cl2 occur? Yes, when the mixture is irradiated with UV light
A standard Newman projection represents how many carbons? 2
What causes the free rotation around the C-C bonds in ethane? the sigma bond
gauche conformation causes what sort of strain? steric
In methylcyclohexane, which conformation is more stable: the equatorial or axial? equatorial
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.
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
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
what is the common structure of steroids? 3 six membered rings, 1 five membered ring fused together
which cycloalkane is strain-free? cyclohexane, b/c it adopts puckered chair conformation
Which type of radicals do NOT form? Phenyl
how do you determine stability of a carbocation? stability increases from primary to tertiary
what is the hydration reaction? water adds to alkenes to yield alcohols
in these acidic reactions, what do you look for? the spot with most carbons attached
what is the first step with acidic hydration and alkene/ring? it degrades the alkene to an alkane
whats second step with acidic hydration? H2O comes to the rescue
in radical RXNS, what can be a terminating step? when 2 radicals come together to form a stable product
in radical substitution: which is selective: chlorine or bromine? bromine
in radical substitution: which position types WONT chlorine go after? phenylic and vinylic
are metals more or less EN charged than a carbon? less
if Keq is less than 1 ... the RXN goes in the reverse direction, from right to left
what is Gibbs free energy change? the E change that occurs during a chemical RXN
does Keq tell you the rate of RXN or how fast equilibrium is reached? NO
how can you tell if radical substitution? hv, single blonds, Cl/Br
how can you tell if radical addition? ROOR, HBr, double bond
how can you tell if electrophilic addition? no hv, no ROOR
if you break pi, sigma, sigma and have sigma, sigma sigma, exo/endothermic? exothermic
when asked about acid/base stability, consider: the 4/5 rules, and whether tertiary, primary, etc.
whats the mnemonic for electrophilic addition? most, basic, rescue. you add HBr across the double bond
when delta G is positive, Keq is ... negative
when delta G is negative, which side preferred? right side
what is the gauche value between CH3 and Br on Newman projection? 0.3
What is the gauche value between Ch3 and CH3 on Newman projection? 0.9
when you think of thermodynamic stability, think.... internal double bonds more stable than external, and, the more carbons on it, the more stable.
if multiple carbocations could form...which one do you choose? the more stable one, based on the ranking 3>2>1..
why is it that usually the first carbocation intermediate is a slow transition? because it does not obey octet rule
break weak bonds, form strong bonds: ____thermic exothermic
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
how many transition states in electrophilic addition? 2
what is "bromination"? electrophilic addition with Br2
in one line, what happens with electrophilic addition? you add ___ across the double bond
which electrons are relatively open to attack? pi electrons in a pi orbital
Name a superbase: LiCH3
Name some polar protic molecules: H2O, D2O
another last way to evaluate side preferred: can tell which is stronger acid/base by, which one more likely to donate protons..etc.
recap: how to tell which side preferred? stability rules, stronger acid/base, the trend
least acidic protons are : methylic
protic conatin which bonds? O-H or N-H
all transition metal cations are Lewis ___ acids. Al, B, Magnesium ion
when forming a standard carbocation, the formal charge will want to reside on the most alkyl substituted side. (b/c more stable)
the energy profile goes down..due to: progressive obeying of octet rule
what is LDA? N with two isopropyls attached
Name 2 basic nucleophiles: NaOH, LiNH2
Name 2 acidic non-nucleophiles: H2SO4, H3PO4
CH3MgBr is a ___ Superbase!
a strong acid has a stable ___ conjugate base
external double bonds: more or less stable than internal? less stable (more unstable)
greater alkyl substitution, the __ stable the double bond more stable
all transition metal cations are: Lewis acids
what does LDA do? dehydrohalogenates
what else dehydrohalogenates? NaNH2 with acetone
Created by: kay21