Organic Chem Chapter 6 – Flashcards
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what type of reaction
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nucleophilic substitution reaction or methyl transfer reaction
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name
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phenyl halide or aryl halide
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...
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vinylic halide
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name
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6.1 (a) cis-I-Bromo-2-methylcyclohexane
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(b) cis-1-Bromo-3-methylcyclohexane
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(c) 2,3,4-Trimethyllieptane
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Alkyloxonium ion
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Consequently, the carbon-halogen bond length increases and carbon-halogen bond strength decreases as we go down the periodic table
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true
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1 step; Favoured in polar aprotic solvents; Most stable 1 > 2 > 3 Least stable; rate = k[Nu][RX]; Optically active/inverted products
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SN2 reaction
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A backside attack occurs when a concerted displacement of one nucleophile by another on a sp3 hybrid atom.
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SN2 reaction
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all bond breaking and bond making occurs in a single step
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concerted reaction
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reactions that release energy
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exergonic
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chemical reaction; requires energy to proceed.
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endergonic
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Two step process where the first step is a carbo cation formed and the second step is the reaction of the nucleophile.
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SN1 reaction
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2 Steps; Favoured in polar protic solvents; Most stable 3 > 2 > 1 > methyl Least stable; rate = k[RX]; racemic products; favoured with the use of bulky nucleophiles
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SN1 reaction
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when two hydrogens are attached to a carbon with 2 different groups
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enantiotopic hydrogens
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# of pi bonds and rings in an alkene
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degree of unsaturation
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In chemistry refers to partial conversion of one enantiomer into another, which often occurs in SN1 substitution.
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Racemization
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rank them
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A solvent containing a hydrogen easily lost as a proton. Examples are water and most alcohols.
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protic solvent
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To impede or hamper the function or activity of: hinder, to impede, hold back
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encumber
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a compound formed by solvation (the combination of solvent molecules with molecules or ions of the solute)
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solvate
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solvents that do not perform H-bonding
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Aprotic solvents
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The rates of SN2 reactions generally are vastly increased when they are carried out in polar aprotic solvents. The increase in rate can be as large as a millionfold.
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true
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Use of a polar protic solvent will greatly increase the rate of carbocation formation of an alkyl halide in any SN1 reaction because of its ability to solvate cations and anions so effectively.
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true
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ability to dissolve polar compounds
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dielectric constant
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Water is the most effective solvent for promoting ionization, but most organic compounds do not dissolve appreciably in water. They usually dissolve, however, in alcohols, and quite often mixed solvents are used. Methanol-water and ethanol-water are common mixed solvents for nucleophilic substitution reactions.
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notes
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the best leaving groups are those that can be classified as
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weak bases after they depart.
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best leaving group for acidity
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1
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substrate
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2
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nucleophile
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delocalization of electrons by overlap of carbon-hydrogen or carbon-carbon sigma bonds with an empty p orbital
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Hyperconjugation
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a reaction between a compound and the solvent at which is dissolved
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solvolysis
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Vinylic and phenyl halides are generally unreactive in SN1 or SN2 reactions
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true
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an elimination in which the two atoms lost are a hydrogen atom and a halogen atom
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Dehydrohalogenation
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x
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beta carbon
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y
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alpha carbon
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what type of reaction
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E2
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draw
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name reaction
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sn1
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name reaction
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Elimination reaction
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nucleophile better for E2 or SN2
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E2
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Use of a weakly basic ion such as a chloride ion (Cl) or an acetate ion (CH3CO2 ) or a weakly basic and highly polarizable one such as Br, I, or RS increases the likelihood of substitution (SN2).
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True
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If an elimination product is desired from a tertiary substrate, it is advisable to use a strong base so as to encourage an E2 mechanism over the competing E1 and SN1 mechanisms
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true
