Alkenes and Alkynes - Catalytic Hydrogenation

These flashcards cover key concepts related to alkenes and alkynes in the context of catalytic hydrogenation, including the types of catalysts used, specific reactions, and mechanisms.

What types of catalysts are used in catalytic hydrogenation?

Heterogeneous (adsorbed on solid support) and Homogeneous (soluble in reaction medium) catalysts.

What are some common transition metals used as catalysts in hydrogenation reactions?

Pt, Pd, Ni, Ir, Rh, and Ru.

What is the reactivity order of transition metals in hydrogenation?

Pt > Pd, Rh = Ru > Ni.

What is the risk associated with H₂ + O₂ + Pd/C?

Can ignite!

What are the general trends observed in the rate of reduction with diimide?

Rate increases with increasing strain and decreases with increasing substitution.

What is Wilkinson's catalyst primarily used for?

Asymmetric hydrogenation.

What is the feature of Crabtree's catalyst in hydrogenation reactions?

It is strongly directed by the presence of hydroxyl groups.

What does asymmetric hydrogenation achieve?

It adds two atoms of H to a target molecule with 3-dimensional spatial selectivity.

What is the most successful asymmetric catalyst derived from?

2,2’-bis(diphenylphosphino)-1,1’-binaphthyl (BINAP).

What does the term 'Lindlar’s catalyst' refer to?

A catalyst used for stereospecific reduction of alkynes.

Which reducing agent is much less reactive than lithium aluminum hydride (LAH)?

Trialkoxyaluminum hydrides.

What is the observed selectivity in sodium borohydride reductions?

Selective reducing agent that reduces aldehydes and ketones to alcohols.

What does the Felkin-Anh model minimize in substrate interaction?

Steric and torsional strain.

In the context of reduction reactions, what do electron-donating groups (EDG) promote?

Direct overall reduction.

What is a key aspect of the Cram's Rule?

Nucleophile addition occurs at the least hindered site.

What do bulky groups affect in chemical reactions involving chelation?

Stop chelation from occurring.

What is the significance of the Burgi-Dunitz angle?

Helps describe the angle at which nucleophiles attack carbonyls.