Chapter 15 Organometallic Compounds Flashcards
Can we use Organolithium reagents under atmospheric oxygen and moisture?
No, they react rapidly with atmospheric oxygen/moisture. Instead, we use them under an inert atmosphere of N2 or Ar
How are carbon-metal bonds usually described?
As polar covalent (when atoms share electrons but one pulls more than the other)
What is the common name for organomagnesium compounds?
Grignard Reagents
What is the key feature of many organometallic compounds?
The carbon bears a partial negative charge, therefore it acts as a base and nucleophilic
How are organomagnesium (Grignard) reagents prepared?
reacting alkyl, aryl, or alkenyl halides (chlorides, bromides, and iodides, NOT fluorides) with a slight excess of magnesium metal in an ether solvent -most commonly diethyl ether or tetrahydrofuran (THF)
How are organolithium compounds prepared?
They are prepared by reacting an alkyl, aryl, or alkenyl halide with two equivalents of lithium metal. (Li=+1)
What is the general formula of organomagnesium compounds / Grignard reagents?
R-Mg-X
Where R is an organic group, Mg is magnesium, and X is a halogen
What is the general formula of an organolithium compound?
R - Li
Where R is an organic group, Li is lithium
What is a carbanion?
An ion in which carbon has an unshared pair of electrons and bears a negative charge
What solvents do we use for organolithium reagents?
We dissolve them in nonpolar hydrocarbon solvents such as pentane
What are the functional groups that Grignard and Organolithium reagents CANNOT be prepared from because they would “self destruct”?
- R2NH (1* and 2* amines)
- Terminal alkynes
- ROH (Alcohols)
- ArOH (Phenols)
- RSH (Thiols)
- RCOOH (Carboxylic acids)
- HOH (Water)
What is oxirane?
Another name for an epoxide. Consists of oxygen and 2 carbons together in a ring.
What are the solvents used to deprotonate a negative oxygen that was the result of an organometallic compound reacting with an epoxide/oxirane?
We usually use HCl/H2O but in general, anything that is an acid that would give away an H+ works. It changes the O- to an OH (Alcohol)
What is the common name for Lithium Diorganocopper reagents?
Gilman reagents
How are Lithium Diorganocopper (Gilman) reagents prepared?
By treating an organolithium compound with copper (1) Iodide
What do Gilman reagents consist of?
Gilman reagents consist of 2 organic groups associated with a copper (1) ion giving a negatively charged species as the counterion
TRUE OR FALSE: Only ONE of the Gilman-reagent groups is transferred in the reaction
True
Coupling Lithium Diorganocopper (Gilman) with a vinylic halide does what to the stereochemistry?
It is stereospecific and therefore preserves the configuration of the carbon-carbon double bond
What is a carbene?
Neutral molecules that contain a carbon with only 6 valence electrons– their organometallic-compound equivalents are called carbenoids
What is the hybridization of carbenes?
They are sp2 hybridized with an empty 2p orbital and a lone pair in one sp2 hybrid orbital
Why are carbenes such as methylene not used for synthesis?
It is too reactive!
Dichlorocarbene and the Simmons-Smith reagent react stereospecifically with alkenes to give..?
cyclopropanes
