ACS Organic Chemistry II Final Examination – Flashcards
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(E) isomers vs. (Z) isomers. Which one is observed when the higher ranked molecules are on the same side? opposite?
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highest on same side: Z highest on opposite sides: E
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Electron-withdrawing groups are what type of directors? What is the one and only exception?
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Meta (deactivators) Halogens
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If the atom directly attached to the aromatic ring has lone pairs what type of director is it? what if it does not have lone pairs?
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lone pairs: activating, ortho, para director no lone pairs: deactivating, meta director
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When are the terms ortho, meta, para used?
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when there are 2 substituents on the aromatic ring
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In IUPAC naming, what is NH2 on a phenyl ring referred to as?
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aniline
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If there is a NO2 group present, what IUPAC prefix will also be evident?
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nitro
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What is the predicted reaction? 1º alkyl halide with a strong base? weak base? poor nucleophile?
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strong base: Sn2 favored but E2 with strong non-nucleophilic bases weak base: Sn2 poor nucleophile: no reaction
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What is the predicted reaction? 2º alkyl halide with a strong base? weak base? poor nucleophile?
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strong base: mostly E2 strong non-nucleophilic bases: mostly Sn2 poor nucleophile: Sn1/E2 (slow) in polar, protic solvents
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What is the predicted reaction? 3º alkyl halide with a strong base? weak base? poor nucleophile?
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strong base: E2 strong non-nucleophilic bases: Sn1/E1 in polar protic solvents poor nucleophile: Sn1/E1 in polar, protic solvents
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What is the configuration of the product in the base-catalyzed hydrolysis of (R)-1-choloro-1-deuteriobutane?
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(S)-1-deuterio-1-butanol (Sn2)
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Where is the largest molecule on the periodic table?
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Bottom lefthand corner
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Nucleophilic strength increase with increasing what?
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atomic size
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Which alkyl valid would you expect to undergo Sn1 hydrolysis most rapidly? I, Br,Cl, or F?
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I
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In which reaction is a racemic mixture obtained? In which reaction is an inversion of chirality obtained?
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inversion: Sn2 racemic mix: Sn1
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Cleavage of an ether usually requires a strong acid that has a conjugate base which is a strong nucleophile, such as...? Depending on the type of alkyl group, the acid reaction with the halide ion produces what?
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HBr HI alkyl halide and an alcohol
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When chirality rotates clockwise the chirality is...
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R
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When chirality rotates counterclockwise the chirality is...
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S
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A solution containing equal amounts of both enantiomers is called a..?
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racemic mixture
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A meso compound contains multiple __________ centers but is nevertheless ________ because it possesses reflection symmetry
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chirality achiral
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For each chirality center Fischer projection - the horizontal lines are considered to be coming _______ of the page and the vertical lines are considered to be going ______ the page _
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horizontal - coming out of the page (towards you) vertical - going out of the page (away from you)
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A racemic mixture of enantiomers is optically _________.
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inactive
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Based off chirality, how can you tell if two molecules are enantiomers?
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If they contain the same molecules but one is S and the other is R
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How do you convert a fischer projection to a wedge and dash diagram?
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1. place lowest priority on dash 2. place highest priority up
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The _____________ a molecule is, the better/stronger nucleophile it is
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larger
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Which type of reaction involves a carbocation intermediate?
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Sn1
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Which type of reaction involves a transition state
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Sn2
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What is the rate determining step in an Sn1 reaction?
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the loss of the leaving group to form the intermediate carbocation.
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What is the rate determining step in an Sn2 reaction?
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the concentration of substrate and the nucleophile
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which reaction will occur if the substrate is 1º?
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Sn2
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which reaction will occur if the substrate is 3º?
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Sn2
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Nucleophiles can behave as bronsted-lowry ________ because of their ability to pick up a H+
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bases
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E2 reactions occur in ________ step(s) E1 reactions occur in ________ step(s)
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E2: 1 step E1: 2 steps
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Which elimination reaction has a unimolecular rate law determination?
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E1
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What does the rate of an E1 reaction depend upon?
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the concentration of the substrate only (unimolecular)
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Which elimination reaction has a bimolecular rate law determination?
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E2
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What does the rate of an E2 reaction depend upon?
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the concentration of the substrate and the base (bimolecular)
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What is the rate determining step in an E1 reaction?
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the formation of the carbocation
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What is the rate determining step in an E2 reaction?
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concerted (bimolecular) happens all at once
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Which elimination reaction requires a strong base?
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E2
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Which elimination reaction requires the stereochemistry of the hydrogen to be removed to be anti to the leaving group
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E2
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The more substituted product is called the..?
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Zaitsev product
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The less substituted product is called the..?
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Hoffmann product
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Which isomer is more stable than the other: E or Z?
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E
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List common base only reagents
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NaH DBN or DBU tertbutyl (KO+) triethyl amine (Et3N)
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How do all base only reagents reactions proceed (1º, 2º, 3º)
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E2
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HOCH3
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weak nu weak base
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List the two ways 2 water molecules can be added across an alkene in a syn addition manner
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1)KMnO4 2)H2O or 1)OsO4 2) H2O2
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List the reagents necessary to add two water molecules across an alkene in an anti fashion
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MCPBA, H3O+
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The majority of E2 eliminations require a transition state conformation in which the B-hydrogen atom and the leaving group are _____ to each other
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anti
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T/F conjugated alkenes are more stable and favored in E2 reactions
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True
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NaCC(R)
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Strong nucleophile/strong base
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Why would concentrated hydrobromic acid be an inappropriate catalyst for the dehydration of alcohols
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Because the conjugate base (Br-) is a good nucleophile and it would attack the carbocation to form an alkyl bromide
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To double the volume of the solvent, you would multiply the reaction rate by a factor of what?
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1/4
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Under basic conditions, nucleophiles will attack the epoxide at the _______ substituted position
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least
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under acidic conditions, the epoxide becomes __________ and then the nucleophile attacks the more ________ carbon
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protonated substituted
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primary alcohol treated with PCC yields? secondary alcohol treated with PCC yields?
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1º = aldehyde 2º = ketone
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What two reagents can be used to convert a primary alcohol into a carboxylic acid?
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KmNO4 or Na2Cr2O7/H2So4
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What reagent can be used to reduce an ether to an alcohol?
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1) LiAlH4 2) H2O
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What reagent can be used to reduce a carboxylic acid to an alcohol?
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1) LiAlH4 2) H2O
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What two reagents can be used to reduce aldehydes and ketones to alcohol?
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NaBH4 or 1)LiAlH4 2)H2O
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What are the two rules for Diels Alder reactions?
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1. The diene must always be in the "s-cis" conformation 2. Stereochemistry in the dienophole is always preserved
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Under normal Diels Alder conditions, which product dominates?
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Endo (everything on wedge or everything on dash)
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On the chair conformation, which way does endo point? exo?
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endo = down exo = up
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Besides H2O, H30+ what is another way to add OH markovnikov across an alkene?
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Hg(OAC)2, H2O followed by NaBH4
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What is the stereochemistry for water being added anti-markovnikov?
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syn addition
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Br2 adds bromines in what fashion across an alkene?
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anti addition
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What is formed when an alkene is treated with a peroxyacid? (R'COOOH)
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an epoxide branching from the alkene bond
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What is the FINAL product when an alkyne is treated with H2O, H2SO4 in the presence of HgSO4
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a ketone
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What must you keep in mind with addition reactions?
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METHYL OR PROTON TRANSFER / CARBOCATION REARRANGEMENTS
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Under which set of conditions is a Diels Alder reaction best carried out?
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heating in hexanes
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Which carbonyl compound would exist to the greatest extent as its hydrate when dissolved in aqueous solution? Why?
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An aldehyde would exist at a greater concentration due to electronic and steric effects
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when an ether (acetal) is treated with H2O, H3O+ in the presence of heat, what occurs?
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ketone
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are the reaction conditions TsOH, C6H6 (heat) considered acidic or basic conditions
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acidic
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What can/cannot NaBH4 be used to reduce?
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ketones or aldehydes not esters or carboxylic acids.
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Methyl vinyl ketone is a conjugated ketone that may undergo 1,2 or 1,4 addition. if the nucleophile is strongly basic (LiAlH4, Ch3MgBr, phosphonium ylide) what type of addition occurs? What about if its not as basic (NaCN)? Which type of reagent is more reversible?
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strongly basic: 1,2 addition Not as basic: 1,4 addition Not as basic: NaCN
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List 4 carboxylic acid derivatives starting most reactive to least reactive
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acyl chloride acid anhydride ester amide
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Best way to convert a carboxylic acid to an ester
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SOCl2
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Which type of polymer could be readily prepared by condensation polymerization?
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Any amine containing compound --> peptide
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activator or deactivator: CH3
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weak activator: para, oath director
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conjugation causes a shift to a lower/higher wavenumber?
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lower wavenumber
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strong absorption at 1720
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ketone
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strong band 2500-3300
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OH - carboxylic acid
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broad with spikes 3300
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amine or amide
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3300 sharp
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CH (sp)
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just above 3000
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CH (sp2)
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just below 3000
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CH (sp3)
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2700 ; 2800 both
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aldehyde
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1735 strong
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C=O ester
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1710 very strong
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C=O aldehyde, ketone, or carboxylic acid
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1660 usually strong
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C=N
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1660 moderate to weak
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C=C nonaromatic
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1600
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C=C aromatic
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