Untitled Quiz

Carbocation Rearrangement

• Carbocations can rearrange to form more stable structures
• Methyl shifts are common
• The rearrangement involves a 1,2-shift of a methyl group
• This leads to the formation of a more stable tertiary carbocation
• The rearrangement proceeds through a transition state

Addition of Lewis Acids (Electrophilic Reagents)

• Lewis acids (halogens, boron hydrides, certain transition metal ions) react with the pi electrons of alkenes
• The resulting complexes can rearrange or be attacked by nucleophiles
• This leads to addition products

Oxidation of Alkenes

• Alkenes can be oxidized using oxidizing agents like potassium permanganate (KMnO₄), potassium dichromate (K₂Cr₂O₇), ozone (O₃), and peroxy acids
• Oxidation with potassium permanganate yields glycols (1,2-diols)
• The reaction needs to be carried out under cold conditions

Oxidation of Alkenes by Ozone

• Ozone (O₃) can be used to oxidize alkenes
• This process is called ozonolysis
• The initial product is an ozonide
• Ozonides can be further processed using Zinc (Zn) and acetic acid (HOAc) into carbonyl compounds

Alkynes

• The general molecular formula for an acyclic alkyne is CₙH₂ₙ₋₂
• Each carbon in an alkyne is sp hybridized
• Alkynes can be synthesized from dihaloalkanes through dehydrohalogenation using alkoxide bases
• Applying this concept to vicinal or geminal carbons of a dihaloalkane will yield an alkyne

Reactions of Alkynes

• Alkynes are electron-rich molecules, acting as nucleophiles
• They react with electrophiles
• The addition mechanism is similar to that of alkenes

Addition to Alkynes by Electrophilic Reagents

• Addition reactions to alkynes are even more exothermic than those of alkenes
• They exhibit Markovnikov regioselectivity and anti-stereoselectivity
• The products are substituted alkenes which can undergo further addition reactions

Hydration of Alkynes and Tautomerism

• The addition of water to alkynes requires a strong acid (e.g., sulfuric acid) and sometimes mercuric sulfate
• Unlike alkene hydration, the initial product is an enol
• Enols are unstable and tautomerize rapidly to the more stable keto form

Oxidation of Alkynes

• Oxidation of alkynes using oxidizing agents like potassium permanganate or ozone cleaves the triple bond
• The products are carboxylic acids