Hydrocarbons, Alcohols, and Substitutions
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| alkane physical properties | show 🗑
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| increased MW of alkanes... | show 🗑
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| increased branching of alkanes... | show 🗑
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| show | can occur on some carbon-carbon bonds in a cycloalkane if they are bended away from the normal 109.5 of the sp3 carbon and cause crowding; zero for cyclohexane and increases if ring becomes larger or smaller; less ring strain=lower energy=more stability
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| show | 1. chair - predominates at RT (lowest energy bc two H's on each C are oriented in diff directions)
2. twist
3. boat
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| show | H's projecting outward from the center of the ring; position where substituent position is preferred
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| show | H's projecting up or down; this position is often where crowding occurs with substituents and will create instability/high energy
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| show | alkane reaction with oxygen - violent reactions that need sufficiently large energy of activations; occurs at high temperature, but once generated can be self perpetuating; radical reaction
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| combustion rxn | show 🗑
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| heat of combustion | show 🗑
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| show | addition of halogen to an alkane; its mechanism -- free radical chain reaction; exothermic process
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| show | active, reacting species formed when light or heat hits diatomic halogen homolytically cleave so that each atom retains 1 e' from the broken bond
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| show | 1. initiation - X2 is cleaved to 2 X.'s
2. propagation - X. removes H from alkane -> alkyl radical which can react with X2 to create free radicals & continue the rxn
3. termniation - alkyl radial combines with each other or X.'s combine with each other
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| show | 3 > 2 > 1 > methyl
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| reactivity of halogens (most to least) | show 🗑
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| show | (how selective a halogen radical is when choosing a position on an alkane - will choose the most stable alkyl radical)
I > Br > Cl > F
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| show | results with increased [halogen] where dilute solns result in monohalogenated products bc halogen radical more likely to collide with alkane rather than alkyl halide
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| alkene | show 🗑
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| alkene physical properties | show 🗑
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| show | by elimination rxn (1 or 2 functional groups eliminated/removed to form dbl bond)
eg: ROH dehydration, dehydrohalogenation
OR
catalytic syn addition of alkyne
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| show | E1 rxn, alcohol forms alkene in the presence of concentrated acid
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| show | elminiation rxn where the rate depends on one species (eg: alcohol deyhydration - rate depends on [ROH])
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| steps of R-OH dehydration | show 🗑
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| show | 3 > 2 > 1 > methyl
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| Saytseff rule | show 🗑
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| show | can be E1 (no strong base) or E2 (high concentration of strong, bulky base)
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| show | 1. halogen drops off alkane to result in carbocation
2. weak base abstracts alpha H to form alkene
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| show | (one step) strong base removes H+ resulting in alkene as the halogen drops off
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| show | prevents SN2 rxn but if too bulky Saytzeff rule is violated and the least substitued alkene results
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| show | syn addition to alkene using heterogenous catalyst (H2 on Ni, Pd, or Pt) so that the H and alkene adsorb to sruface of the catalyst; exothermic with high energy of activation
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| heats of hydrogenation | show 🗑
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| oxidation of alkenes | show 🗑
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| oxidation of alkynes | show 🗑
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| electrophillic addition | show 🗑
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| show | e' loving species, least + charge
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| Markovnikov's rule | show 🗑
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| show | happens in the presence of peroxides where the halide, NOT THE H, will add to the least substituted carbon
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| which are the most reactive alkenes in electrophillic addition? | show 🗑
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| concentrated acid and heat help react ___ to ____ | show 🗑
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| dilute acid and cold help react ____ to ___ | show 🗑
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| show | driven by low temp and dilute acid, follows markovnikov's rule (reversal of dehydration of alcohol)
alkene + H2O --> alcohol
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| oxymercuration | show 🗑
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| show | addition from opposite sides of the double bond
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| show | takes the product of oxymercuration with a reducing agent (NaBH4) and base to remove Hg to form an alcohol
4(oxymercuration product) + NaBH4 + 4OH- --> 4R-OH + NaB(OH)4 + 4Hg + 4-OAc
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| hydroboration | show 🗑
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| show | halogen additions to alkenes in the presence of peroxides, hydroboration
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| markovnikov reactions | show 🗑
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| show | formation of vic-dihalide (2 halogens connected to adjacent carbons)via anti-addition
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| benzene | show 🗑
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| ortho positions on benzene ring | show 🗑
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| show | 1,3 or 1,5
directed by e' withdrawing groups
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| show | 1,4 (opposite sides of ring)
directed by e' donating groups
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| show | -O-, -OH, -NR2
(oxygen ion, alcohol, amine with 2 R groups)
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| show | -NO=O, -NR3, -CCl3
(nitro group, amine with 3 R groups and +N, carbon tetrachloride
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| show | -OR
(ether)
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| weakly e' donating | show 🗑
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| moderately e' withdrawing | show 🗑
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| weakly e' withdrawing | show 🗑
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| electron withdrawing group | show 🗑
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| show | when occupying 1 position on the benzene ring, it will activate (makes more reactive) the ring and direct substituents to the ortho and para positions-- stabilizes double bonds bc alkenes withdraw e' through their bonds
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| show | can be unimolecular (SN1) or bimolecular (SN2) which represents the order of the rate law - SN1 rate of substitution depends on 1 molecule and SN2 rate depends on 2 molecules
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| show | -2 steps
-rate = k[S]
-carbocation intermediate
-prefers tertiary carbons
-prefers protic solvents
-produces racemic mixture
-often accompanied by E1 rxns bc Nu:- can act as a base to abstract H+ from carbocation
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| SN2 | show 🗑
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| show | halogen ion drops off substrate creating carbocation -> Nu:- attacks carbocation --> Nu substituted for halogen (both enantiomers)
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| show | Nu:- attacks carbon on one side as the LG breaks free from substrate
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| show | tertiary carbons sterically hinder the nucleophile
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| why don't SN2 rxns typically occur in the presence of a strong base? | show 🗑
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| show | steric hinderance
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| nucleophilicity | show 🗑
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| show | polar solvents that can hydrogen bond, stabilize nucleophile and any carbocation that forms--> increase rate of SN1 and decrease rate of SN2
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| polar aprotic solvents | show 🗑
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| leaving groups | show 🗑
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| physical properties of alcohols | show 🗑
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| show | methyl > 1 > 2 > 3
the conjugate bases that can absorb more (-) charge are more stable and its corresponding acid is stronger **H can absorb (-) charge better than methyl groups**
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| Rxns to synthesize alcohols | show 🗑
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| show | R-MgX (highly polarized carbon metal bond where the carbon is more electronegative than the metal so it takes on a strong partial (-) charge making it a STRONG NUCLEOPHILE AND BASE)
need to be made in ether- incompatible with water
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| show | R-MgX + R-CR=O --> CR3O- - +MgX --> CR3OH + XMgOH
extends C skeleton, will react in similar fashion with C=N, C=-N, S=O, N=O and can deprotonate O-H, N-H, S-H, -C=-C-H
nucelophillic carbon attacks carbonyl and after acid bath, will produce an alcoho
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| show | using NaBH4 or LiAlH4, the H- will attack the carbonyl to reduce aldehydes and ketones to alcohols
only LiAlH4 is strong enough to reduce esters and acetates
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| show | bc the grp attached to the carbonyl of the ester or acetate is a stronger e' donor than an akyl grp or H. by donating e's more strongly, it reduces the (+) charge on the arbonyl making it less attractive to the nucleophile
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| show | thru nucelophillic addition or substitution; the lone pairs on oxygen can attack positive charge
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| oxidation in orgo rxns | show 🗑
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| reduction in orgo rxns | show 🗑
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| show | addition or loss of H+, H2O, HX, etc
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| show | only primary and secondary ROH's can be oxidized (primary -> aldehydes; secondary ->ketones)
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| show | K2Cr2O7
KMnO4
H2CrO4
O2
Br2
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| show | LiAlH4
NaBH4
H2 + pressure
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| show | R-CH2-OH + HX --> R-CH2-OH2 + X- --> R-CH2-X
protonates OH group to make good LG (water) where the alcohol is acting as an electrophile and halogen as the nucleophile; can also be accomplished with P-halides (PBr3, PI3, PCl3 as SN2 mechanism) or SOCl2
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| formation of sulfonate | show 🗑
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| show | -sulfur double bonded to two O's, single bond to one O and one R group
- common ones are tosylates and mesylates
- act as weak bases and excellent leaving groups in SN1 or SN2 rxns
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| pinacol rearrangement | show 🗑
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| pinacol rearrangement mechanism | show 🗑
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| show | relatively non reactive, polar, can only H bond with other componds that have H attached to N, O, or F (not themselves), roughly soluble in water, dissolves organic cmpds easier, has low BP
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| rxns with ethers | show 🗑
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| epoxide | show 🗑
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| show | alkane < alkene < H2 < NH3 < alkyne < aldehyde < alcohol < water < carboxylic acid
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| show | results in -OH group added to most substituted carbon on alkene (markonikov)
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