Ochem Lab Final Answers

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why is the bromine a deactivating group for the EAS reaction
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due to bromines high electronegativity it cant donate electrons into the ring
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why is the nitro group a dectivating group for the EAS reaction
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the nitro group acts as a base in this reaction and is deactivating because it is positvely charged meaning it is an electron withdrawing group and a meta director
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EAS observations
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the liquid mixture went from clear to yellow and clumps of round yellow-white balls collected on spinvane, after filtration white crystals appeared.
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possible identity of isolated product in the EAS experiment
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p-bromonitrobenzene
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write out the complete mechanism for the formation of your product from bromobenzene, be sure to include all arrow pushing, formal charges, and three resonance stabilized intermediates
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provide all the resonancce stablized intermediates for the meta-subsititution, the first one is provided
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explain using resonance why your product is favored over the meta product in the EAS lab
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our product is favored over the meta-product becasue based on the resonance structures our product has the best carbocation as teritary as opposed to the meta-product that has the best carbocation as secondary. therefor due to carobcation stability an attack would be favored at the para position
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write out the planned synthetic reaction, in addition to the starting material and products also include all reagents, catalysts, and solvents
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what is the purpose of sulfuric acid or phosphoric acid used in the acetylation reaction> use equations to help explain this purpouse
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the purpose is to maek the electrophile more electrophillic, takes a hydrogen from a phosphoric acid
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the procedure calls for cautiona ddition of water to the reaction mixture while it is still hot. what prupose does the addition of water serve and why should the addition of water be done while the reaction mixture is still hot, provide an equation
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the purpose of the addtion of th water is to hydrolyze the excess acetitc anhydride and the reaction should be done while hot because if the mixture cools the hydroloysis will slow
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what impurity is most likely to be presentin the sample of aspirin you prepared what effet would this impurity have if the product were intended for human consumption
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the impurity most likely present would be salicylyic acid and if consumed would cause damage to the stomach and digestive system due to high acidity
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upon heating with acid, salicyclic acid can react with another molecule of salicyclic acid what is the structure likely to be
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write the equation for the reaction that occurs when aspirin is hydrolyzed in the body
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Resonance = Stability
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Arrows start at a source of electrons and move to a “lack” of electrons
Think electronegativity
Possible options to move electrons from
1. bond to bond
2. bond to atom
3. atom to bond
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Alkene properties
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Resonance: put the cation on most stable carbon (3 > 2 > 2)
Priority Rules: E/Z::trans:cis (applies to R,S as well)
1. Molecular weight of first atom
2. #1 fails? Molecular weight of second atom, third and so on
3. Multiple bonds? Check book, rule o thumb: more bonds = higher priority
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Acid/Base chemistry (Think HCl: acid and NaOH: base)
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Ranking acidity
1. H bound to most electronegative element
2. Stability of conjugate base/anion (remove H atom)
a. Resonance
b. Induction (proximity of electronegative elements, usually halides)
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Addition
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Breaking a double bond to add two new bonds
new bonds: usually Hydrogen and Electronegative element
WATCHOUT for IMPLIED hydrogens
Common reagents: HCl, HBr, H2O, Br2, etc
Electronegative bond most often goes to most substituted carbon
Stereochemistry depends on reagents
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Substitution
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exchange one atom(group) for another
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SN1
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Rate = k [Electrophile] multi-step
1. Stability of cation
2. Stability of leaving group
3. Reactivity: 3 = fastest > 2 > 1 = slowest
4. Loss of Stereochemistry if started with it
a. R => S and R OR S => R and S
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SN2
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Rate = k[Electrophile][Nucleophile] one-step
1. Sterics = Size gets in the way
2. Stability of leaving group
3. Reactivity: 1 = fastest > 2 > 3 = slowest
4. Inversion of stereochemistry
a. R => S or S => R
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Elimination
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Loss of electronegative atom AND hydrogen to FORM DOUBLE bond
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E1
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Rate = k[Electrophile(pseudo-acid)] multi-step
1. Stable cation
2. Stable leaving group
3. More substituted double bond product
4. Favors more stable of cis/TRANS
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E2
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Rate = k[Electrophile(pseudo-acid)][Base] one-step
1. STRONG BASE
2. Stable leaving group
3. More substituted double bond product
4. Elimination occurs ANTI, which forces stereochemistry
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Carbonyl chemistry
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Focus seems to be largely on nomenclature.
Reactivity: Electronegativity/Resonance
Carbon = electrophile Oxygen = nucleophile/base

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