Organic Chemistry (CHM 221) Chapter8

Trans-2-butene is more stable than cis-2-butene, which is more stable than 1-butene.

E2 reactions exhibit second-order kinetics, where both the alkyl halide and the base are included in the rate equation.

As the strength of the base increases, the rate of the E2 reaction also increases.

<p>Better leaving groups increase the rate of E2 reactions.</p> Signup and view all the answers

<p>Cis isomers have substituents on the same side, causing more steric hindrance than trans isomers, which have substituents on opposite sides.</p> Signup and view all the answers

<p>Both E1 and SN1 mechanisms are unimolecular and involve a carbocation intermediate.</p> Signup and view all the answers

<p>Polar aprotic solvents are preferred for E2 reactions because they help stabilize the transition state and increase the reaction rate.</p> Signup and view all the answers

<p>2-butenes (disubstituted) are more stable than 1-butene (monosubstituted) due to increased substitution leading to greater alkene stability.</p> Signup and view all the answers

<p>An SN1 reaction involves a nucleophile attacking a carbocation, while an E1 reaction involves a base removing a proton to form a pi bond.</p> Signup and view all the answers

<p>Strong bases favor E2 mechanisms, while weaker bases tend to favor SN1 or SN2 mechanisms.</p> Signup and view all the answers

<p>A vicinal dihalide undergoes two elimination reactions to produce a triple bond in the alkyne.</p> Signup and view all the answers

<p>One common base used for synthesizing alkynes is sodium amide (NaNH2).</p> Signup and view all the answers

<p>Good nucleophiles that are weak bases, such as I− and Br−, favor substitution.</p> Signup and view all the answers

<p>Bulky non-nucleophilic bases favor elimination pathways over substitution reactions.</p> Signup and view all the answers

<p>Primary alkyl halides typically favor SN2 reactions, while tertiary alkyl halides favor SN1 or E1 pathways.</p> Signup and view all the answers

<p>Two elimination reactions are required to fully remove two moles of HX and form an alkyne.</p> Signup and view all the answers

<p>Alkenes are classified as mono-alkenes, dienes, and polyenes depending on whether they contain one, two, or multiple double bonds.</p> Signup and view all the answers

<p>Cis isomers have substituents on the same side of the double bond, while trans isomers have them on opposite sides.</p> Signup and view all the answers

<p>Stereoisomers are compounds that have the same molecular formula and connectivity but differ in the spatial arrangement of atoms, commonly seen in alkenes due to their restricted rotation around double bonds.</p> Signup and view all the answers

<p>The stability of alkenes increases with the number of alkyl groups attached to the double bond, as steric effects and hyperconjugation stabilize the double bond.</p> Signup and view all the answers

<p>Dehydrohalogenation involves the elimination of HX from an organic substrate, where a base abstracts a proton from the β carbon while the leaving group departs from the α carbon to form a π bond.</p> Signup and view all the answers

<p>β-elimination is the process where elements are removed from a β carbon along with a leaving group from the α carbon, resulting in the formation of a carbon-carbon double bond.</p> Signup and view all the answers

<p>Common bases such as alkoxides (e.g., RO−) and hydroxides (HO−) are important as they facilitate the removal of elements during the elimination process.</p> Signup and view all the answers

<p>Restricted rotation in alkenes occurs due to the presence of a double bond, leading to the formation of cis-trans isomers based on the spatial arrangement of substituents.</p> Signup and view all the answers

A nucleophile attacks a carbocation, forming a substitution product.

A base removes a proton, creating a new pi bond.

Elimination reaction producing a pi bond (alkene) from a single step.

Two consecutive elimination reactions produce two pi bonds(triple bond).

Base strength is key in determining whether elimination (E1 or E2) or substitution (SN1 or SN2) will occur.

Two elimination reactions create an alkyne from dihalide substrates.

Alkyne synthesis needs stronger bases like NaNH2 or KOC(CH3)3 compared to base needed for alkene.

The structure of the alkyl halide (primary, secondary, tertiary) and the nucleophile/base influence the reaction mechanism.

A chemical process where atoms or groups are removed from a molecule, leading to the formation of a new bond.

A specific elimination reaction where a hydrogen atom (H) and a halogen atom (X) are removed from a molecule.

The carbon atom adjacent to the carbon attached to the leaving group (halogen) in a dehydrohalogenation reaction.

A negatively charged oxygen compound (like RO-) used in elimination reactions.

A type of covalent bond formed by the side-by-side overlap of atomic orbitals, resulting in electron density above and below the bond axis.

Hydrocarbons containing a carbon-carbon double bond.

A type of hybridization where a carbon atom uses one s orbital and two p orbitals to form three sp2 hybrid orbitals

A molecular geometry with three atoms bonded to a central atom, forming a flat triangle with 120-degree bond angles.

An alkene is 'disubstituted' when two carbon atoms, each directly bonded to the double bond, are also bonded to other carbon atoms. This increases stability compared to 'monosubstituted' alkenes with only one carbon bonded to the double bond.

Trans-2-Butene has the methyl groups on opposite sides of the double bond, minimizing steric hindrance and resulting in less crowding. Cis-2-Butene has the methyl groups on the same side of the double bond, leading to more steric strain.

In an E2 reaction, a base removes a proton from a carbon adjacent to a leaving group. The leaving group departs simultaneously, forming a double bond (alkene).

The E2 reaction is concerted because all bond breaking and formation occurs in a single step. The base removes a proton, the leaving group departs, and the double bond forms simultaneously.

Both the alkyl halide and the base are involved in the rate-determining step of an E2 reaction. This means the rate of the reaction depends on the concentration of both the alkyl halide and the base.

Strong bases like -OH and -OR increase the rate of E2 reactions. The stronger the base, the faster the proton removal step, leading to a quicker reaction.

DBN (diazabicyclononane) is a bulky, non-nucleophilic base that favors elimination reactions. It's less likely to attack the carbon where the leaving group is attached, promoting the removal of a proton instead.

Better leaving groups lead to faster E2 reactions. Polar aprotic solvents also increase the rate of E2 reactions by stabilizing the transition state and promoting the formation of the alkene.