Short Answer Test Question

Question:
Fill in the missing pieces of this Aldol Reaction.

Solution:
If LDA is used at low temperatures, the kinetic enolate is generated and can think react with an aldehyde. The full reaction is shown below.

Hell-Volhard-Zelinsky Halogenation

A Hell-Volhard-Zelinsky Halogenation is a reaction that halogenates carboxylic acids at the alpha carbon. This reaction takes place in the absence of a halogen carrier and is initiated by the addition of a catalytic amount of PBr3. One molar equivalent of Br2 is then added. The carboxylic OH is replaced with a bromide because of the PBr3 that was added. The result is a carboxylic acid bromide. This allows the acyl bromide to tautomerize to an enol so that it can readily react with the Br2 in order to brominate a second time at the alpha position. This reaction is named after the three German chemists. The general reaction looks like this:

I found a Hell-Volhard-Zelinsky Halogenation reaction involving cycloalkane carboxaldoxime carbamates. These compounds are useful as pesticides and have very excellent miticidal activity. These compounds are prepared by the alpha halogenation of cyclic carboxylic acids under slightly modified Hell-Volhard-Zelinsky conditions. Esterification to give the cyclic alpha halocycloalkanecarboxylic acid easter follows. The active halogen is displaced with sodium alkyl mercaptide in alcohol to produce the alkylthio ester. The hydrolysis of the ester is followed by reacting the hydrolyzed product with thionyl chloride which give the reactive acid chloride. The acid chloride is changed into the aldehyde. The aldehyde then reacts with the hydroxylamine hydrochloride in a base and gives a corresponding oxime. The oxime can be carbamoylated with the suitable reagents to form the final insecticidal agent. A picture of the synthesis follows:

Sources:

• http://en.wikipedia.org/wiki/Hell-Volhard-Zelinsky_halogenation
• http://www.google.com/patents?hl=en&lr=&vid=USPAT3721711&id=9yMuAAAAEBAJ&oi=fnd&dq=Hell-Volhard-Zelinsky+halogenation&printsec=abstract#v=onepage&q=Hell-Volhard-Zelinsky%20halogenation&f=false

Isoamyl acetate

General Information:
This ester is more commonly known as banana oil. It's formula is CH3COOCH2CH2CH(CH3)2. The molecular weight is 130.19. In the physical state it is clear and colorless with a banana-like pr pear-like odor. It's melting point is -78C and it's boiling point is 142C. Isoamyl acetate is slightly soluble in water but is very soluble in Ethyl butyrate and Isoamyl butyrate. It is used to confer banana flavor in foods. It is also used as a solvent for some varnishes and lacquers. It is also a honey bee pheromone that is used to attract large groups of honey bees to a small area. It was extensively used in the aircraft industry for stiffening and wind-proofing fabric flying surfaces. It is also used to test the effectiveness of respirators or gas masks because of its intense, pleasant odor and low toxcity.  Acetates have characteristic fruity odors. They are used as component of perfumes and flavorings. They are used as chemical intermediate to manufacture pharmaceuticals, synthetic flavorings, cleaners, and other organic compounds. 


Isoamyl actate:
This is a picture of the structure of Isoamyl acetate:

Production:
Isoamyl acetate is prepared by the acid catalyzed reaction (Fischer esterification) between isoamyl alchol and glacial acetic acid as shown in the reaction equation below. Typically, sulfuric acid is used as the catalyst. Alternately, an acidic ion exchange resin can be used as the catalyst. 

References:
http://www.chemicalland21.com/specialtychem/perchem/ISO-AMYL%20ACETATE.htm
http://en.wikipedia.org/wiki/Isoamyl_acetate

Grignard Reagent

We are discussing Grignard Reagents in class. A Grignard Reagent is an alkyl- or aryl- magnesium halide that acts as a nucleophile and attacks electrophilic carbon atoms that are present within polar bonds to yield a carbon-carbon bond. Below shows the reaction used to make 4-nonylbenzoic acid:

  

 The Grignard Reagent is used in step A. The addition of the nonylmagnesium bromide causes an immediate color change from red to black-violet. The final product of that reaction is 4-Nonylbenzoic acid methy ester. The Grignard reagent is highlighted below:

A Grignard reaction yields new C-C bonds. There were 8 new C-C bonds formed in Step A. They are highlighted below:

The group performing this experiment developed an alternative method for alkyl-(hetero)aryl- as well as aryl-heteroaryl cross coupling reactions catalyzed by iron salts. They discovered that the expensive noble metal catalysts can be replaced by cheap, air stable, commercially available and toxicaologically benign salts without any loss in efficiency. The reactions are usually carried out under "ligand free" conditions using inexpensive Grignard reagents as the preferred coupling partners. They also found due to the efficiency with which the iron catalysts activate the C-Cl bond, several functional groups are tolerated that normally would react with a Grignard reagent. Feel free to read more by clicking on the source listed below! :)

Source:
http://orgsyn.org/orgsyn/default.asp?formgroup=basenpe_form_group&dataaction=db&dbname=orgsyn