Presentasi Organik

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Nama Anggota:Muhammad Iqbal Syauqi 1306442151Sela Viviyani 1306366136Maghfira Fauzia 1306365890Aisyah Nadila 1206219376Intan Rahayu 1206223695Sriwahyuni Madya S. 1206220485

CARBOXYLATE : ENOLATE

Enol Enolate formation Claisen Condensation

Cross Claiser Condensation Dieckmann Condensation

Ester Malonate

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Substitusi-αdan

Kondensasi Enol - Enolat

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Posisi α Karbon di sebelah gugus karbonil

ditetapkan seperti berada di posisi α Substitusi elektrofilik terjadi pada

posisi ini melalui sebuah enol atau ion enolat

Enol

Enolat Enolat terbentuk saat suatu basa

menghilangkan proton pada karbon-α ke gugus karbonil.

Enolat nukleofilik

Claisen Condensation

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CROSS CLAISEN CONDENSATION

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Reaksi claisen bersilang untuk melakukan reaksi Claisen

dengan dua komponen karbonil yang berbeda sebagai bahan awal

Reaksi Claisen antara dua senyawa karbonil yang berbeda disebut reaksi Claisen bersilang.

Sebuah disilangkan Claisen adalah secara sintetis yang berguna dalam dua contoh yang berbeda:

1. Apabila ada dua ester dan salah satunya punya α hidrogen biasanya hanya satu produk yang terbentuk

2. Reaksi antara keton dan ester, enolat ini selalu dibentuk dari keton dan reaksi bekerja dengan baik ketika ester tidak memiliki α hidrogen . maka produk dari reaksi claisen

bersilang ialah senyawa β-dikarbonil bukan β-keto ester

Reaksi antara keton dan ester ialah penting karena memberikan akses mudah untuk membentuk β keto ester , yang merupakan bahan awal yang berguna dalam sintesis ester asetoasetat

Dalam reaksi ini, cl- lebih mudah dihilangkan daripada –Oet, karena Cl adalah leaving grup yang baik..

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Dieckmann Condensation Reaction

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Background The Dieckmann Condensation is an intramolecular

variant of the Claisen Condensation. The reaction is most commonly used to prepare 5 or 6 membered ring ß-keto esters.

The formation of 5 membered rings tends to be faster than 6 membered rings, although the 6 membered ring products are generally more thermodynamically stable.

Ring formation becomes progressively more difficult to accomplish as the ring size of the desired product increases.

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: Reaction and Mechanism

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Application :

The acidic hydrogen between the two carbonyl groups is deprotonated in step four. Protonation with a Brønsted-Lowry acid (H3O+ for example) re-forms the β-keto ester. This deprotonation step is the driving force for this reaction.

Owing to the steric stability of five- and six-membered ring structures, these will preferentially be formed. 1,4- and 1,6 diesters will form five-membered cyclic β-keto esters, while 1,5- and 1,7 diesters will form six-membered β-keto esters.

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The Dieckmann Condensation generally cannot be used to prepare small, highly strained ring systems. Rather than form a three membered ring, diethyl succinate undergoes an intermolecular Claisen Condensation followed by a Dieckmann Condensation to afford the six membered ring compound instead of reacting to form the three membered ring ß-keto ester as shown following.

The reaction typically employs the sodium alkoxide of the alcohol that corresponds to the alcoholic moiety of the ester functional groups. The reaction can also be promoted by the use of one equivalent of sodium hydride and a catalytic amount of the corresponding alcohol.

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Conclusion

The base-catalyzed intramolecular condensation of a diester. The Dieckmann Condensation works well to produce 5- or 6-membered cyclic ß-keto esters, and is usually effected with sodium alkoxide in alcoholic solvent

Sintesis Ester Malonat

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Reactions of Enolates—Malonic Ester Synthesis• The malonic ester synthesis results in the preparation of -

substituted carboxylic acids having two general structures:

• The malonic ester synthesis is a stepwise method for converting diethyl malonate into a carboxylic acid having one or two alkyl groups on the carbon.

Reactions of Enolates—Malonic Ester Synthesis• Thus, the malonic ester synthesis converts diethyl malonate

to an -substituted carboxylic acid in three steps.

Reactions of Enolates—Malonic Ester Synthesis• Heating diethyl malonate with acid and water hydrolyzes

both esters to carboxy groups, forming a -diacid (1,3-diacid).

• -Diacids are unstable to heat and decarboxylate resulting in cleavage of a C—C bond and formation of a carboxylic acid.

Reactions of Enolates—Malonic Ester Synthesis• The net result of decarboxylation is cleavage of a C—C

bond on the carbon, with loss of CO2.

Reactions of Enolates—Malonic Ester Synthesis• To use the malonic ester synthesis, you must be able to determine

what starting materials are needed to prepare a given compound—that is, you must work backwards in the retrosynthetic direction. This involves a two-step process:

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References:

http://www.wikipidida.com. http://blog.para-gen.com. www.organic- chemistry.org/namedreacti...