Organic mechanisms Flashcards
hard questions
What behavior of a hydrogen ion allows it to act as an electrophile?
Accept a pair of electrons
Electrophiles are species that seek electrons to form bonds.
What is the primary reaction pathway for 2° and 3° alcohols undergoing substitution?
2° = muchopmie sub + ariminarion; 3° = triminanon
This indicates the types of substitution mechanisms favored by different alcohols.
Why can an OH- ion behave as a nucleophile in the reaction with 2-iodobutane?
The lone pair of electrons on the oxygen
Nucleophiles are electron-rich species that donate electron pairs.
Why are major and minor products produced in the reaction between but-1-ene and hydrogen bromide?
But-1-ene is an unsymmetrical alkene; the intermediate can be primary or secondary carbocation. Secondary carbocations are more stable than primary carbocations.
The stability of carbocations influences the major product formed.
What does a curly arrow represent in reaction mechanisms?
The movement of a pair of electrons
Curly arrows illustrate the flow of electron pairs during chemical reactions.
Define homolytic fission.
Covalent bond is equally splitting forming radicals
This process results in the formation of two radicals from one bond.
Write the overall equation for the reaction between chlorine and methane.
CH4 + Cl2 → CH3Cl + HCl
This reaction illustrates the substitution of hydrogen in methane by chlorine.
Why do alkenes readily react with chlorine compared to alkanes?
Alkenes have double bonds; they are electron-rich, forming an induced dipole in chlorine
The presence of double bonds in alkenes makes them more reactive towards electrophiles.
Explain why the major and minor products formed from the reaction are not produced in equal amounts.
The major product is formed form a tertiary carbocation.
Tertiary is more stable than primary
More alkyl groups the more spread out the positive charge is
What is the major product formed from?
A tertiary carbocation
Tertiary carbocations are more stable than primary ones due to greater alkyl group stabilization.
Why do hydroxide ions behave as nucleophiles in the reaction?
The hydroxide is attracted to the positive carbon
This occurs because the Cl atom is more electronegative, making the carbon partially positive.
Why does stereoisomerism not arise in the product?
Both carbon atoms in the C=C double bond do not have 2 different groups attached.
Name the reagent and a key condition necessary to ensure a high yield of alkene.
KOH - high temperature/ concentrated/ ethanolic
Why can cyanide act as a nucleophile?
It has a lone pair of electrons on the carbon atom
There is also a full negative charge on the carbon.
Why does a reaction not require a high temperature?
Tertiary alcohols favor elimination because tertiary carbocations are more stable than secondary/primary.
Why are both major and minor products produced in the reaction?
The intermediate would contain a tertiary carbocation
The minor product comes from a secondary carbocation, which is less stable.
Why can halogen molecules react with alkenes?
High electron densities in C=C bond cause an induced dipole in X2.
How can the conditions be altered to produce a high yield of trichloromethyl benzene?
Using excess chlorine increases the chance of free radicals.
Why would a reaction containing 2-iodo, 2-methylbutane be quicker than using 2-chloro, 2-methylbutane?
C-Cl bond is stronger; AR of Cl is less than iodine
The bond polarity in C-Cl is greater due to a larger difference in electronegativity.
