Examples of ester in the following topics:
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- Esters are ubiquitous.
- Polymerized esters, or polyesters, are important plastics, with monomers linked by esteric units like this:
- Ester names are derived from the parent alcohol and acid.
- Cyclic esters are known as lactones.
- Esters react with nucleophiles at the carbonyl carbon.
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- Since the carbene moiety of a Fischer carbene has many of the characteristics of a carbonyl group, it is instructive to begin our survey with some ester-like transformations.
- The first diagram displays a few carbonyl-like reactions, which mimic organolithium addition to ketones (eq. # 1), ester amination (eq. # 2), the Wittig reaction (eq. # 3) and alpha-carbon alkylation (eq. # 4).
- In most cases the carbene is a stronger activating group than the corresponding ester.
- The last equation shows an unusual case of thermal [2+2]-cycloaddition, which does not take place with the ester equivalent.
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- Esters undergo a similar transformation called the Claisen Condensation.
- Greek letter assignments for the ester products are given in blue.
- The specific alkoxide base used should match the alcohol component of the ester to avoid ester exchange reactions.
- Esters usually serve as the electrophilic acceptor component of the condensation.
- There are three ester functions, each of which has at least one alpha-hydrogen.
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- Esters are the most common carbonyl reactants, since they are cheaper and less hazardous to use than acyl chlorides and anhydrides.
- Most esters react with organometallic reagents to give 3º-alcohols; but formate esters (R=H) give 2º-alcohols.
- The second equation demonstrates the low reactivity of organocadmium reagents, inasmuch as the ester function is unchanged.
- Esters react with organometallic reagents to give 3º-alcohols; formate esters (R=H) give 2º-alcohols
- Reaction with acyl chlorides, anhydrides and esters leads to alcohol products
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- Waxes are esters of fatty acids with long chain monohydric alcohols (one hydroxyl group).
- Natural waxes are often mixtures of such esters, and may also contain hydrocarbons.
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- The chemistry of phosphines and the related phosphite esters is dominated by their strong nucleophilicity and reducing character.
- Phosphite esters react in the same manner, but the resulting phosphonium salts (shaded box) are often unstable, and on heating yield dialkyl phosphonate esters by way of a second SN2 reaction (equation 2 below).
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- Esters and nitriles are even weaker alpha-carbon acids than ketones (by over ten thousand times), nevertheless their enolate anions may be prepared and used in a similar fashion.
- Malonic acid esters and acetoacetic acid esters are commonly used starting materials, and their usefulness in synthesis will be demonstrated later in this chapter.
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- Most of the functions are amides or esters, cantharidin being a rare example of a natural anhydride.
- Cyclic esters are called lactones, and cyclic amides are referred to as lactams.
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- Reactivity: acyl halides > anhydrides >> esters ≈ acids >> amides
- The reaction of an acyl chloride with an alcohol also gives an ester, but this conversion cannot be reversed by adding HCl to the reaction mixture.
- Esters are one of the most common carboxylic derivatives.
- Finally, anhydrides and esters have intermediate reactivities, with anhydrides being more reactive than esters.
- Esters are less reactive acylating reagents than anhydrides, and the ester exchange reaction (#6) requires a strong acid or base catalyst.
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- A pair of radicals is generated by photohomolysis of the weak N–O bond of a nitrite ester.
- This eventually leads to a nitrate ester on the newly functionalized carbon.
- The nitrite ester of an axial oriented 11-hydroxyl group is prepared by reaction with nitrosyl chloride, 2.
- In the presence of oxygen, the corresponding nitrate ester, 6, is produced.