Ethyl acetoacetate 乙酰乙酸乙酯 teaches you Organic spectroscopy… brush up?????

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Ethyl 3-oxobutanoate
Acetoacetic acid ethyl ester
Ethyl acetylacetate
3-Oxobutanoic acid ethyl ester

Ethyl acetoacetate is produced industrially by treatment of diketene with ethanol.

The preparation of ethyl acetoacetate is a classic laboratory procedure.^[2] It is prepared via the Claisen condensation of ethyl acetate. Two moles of ethyl acetate condense to form one mole each of ethyl acetoacetate and ethanol.

Structure: 

IUPAC Name: ethyl 3-oxobutanoate (ethyl acetoacetate)

Analysis: C₆H₁₀O₃: MW = 130.14

The molecule contains an oxygen, and from the analysis, contains two double bonds, carbonyls or rings.
The mass spectrum displays a molecular ion and the base peak represents the formation of the acylium ion, indicating the presence of a methyl adjacent to a carbonyl. The presence of an m-45 peak strongly suggests the presence of an ethoxy group.
The ¹³C spectrum contains six peaks, indicating that all carbons are unique. The quartets at  14 and 24 represent relatively simple methyl groups; the triplets at  59 and 47 represent a CH₂ groups bonded to mildly electronegative groups; the singlets at  207 and 172 are in the carbonyl region, and most likely a ketone or aldehyde ( 207) and an ester ( 172).
The proton NMR shows evidence for an ethyl group and isolated CH₂ and CH₃ groups. The methylene of the ethyl group must be next to an electronegative atom (most likely oxygen) suggesting an -OCH₂CH₃ group. The isolated CH₂ must also be flanked by mildly electronegative groups, and the isolated CH₃ is in the region often observed for methyls adjacent to carbonyls.
The IR is consistent with a simple saturated hydrocarbon, possibly containing two carbonyls (based on the side peak at  1670 cm^–1). The minor peak at 3400 cm^–1 is too small to be an -OH.
The simplest structure which is consistent with all of these data would be a dicarbonyl compound containing an ethoxy residue and a methyl ketone (based on the presence of the acylium ion in the MS).

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1H NMR

The proton NMR has a quartet coupled to a triplet, indicative of an ethyl group. The CH₂ must be adjacent to an electron withdrawing group since it is shifted to  4.1. The two singlets at  2.2 and 3.2 suggest isolated CH₂ and CH₃ groups and the CH₂ must be adjacent to one or more electronegative groups.

 

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13C NMR
¹³C NMR Assignments: 
¹³C NMR Data: q-13.6; q-24.2; t-59.2; t-46.6; s-172.0; s-207.1
The ¹³C spectrum contains six peaks, indicating that all carbons are unique. The quartets at  14 and 24 represent relatively simple methyl groups; the triplets at  59 and 47 represent a CH₂ groups bonded to mildly electronegative groups; the singlets at  207 and 172 are in the carbonyl region, and most likely a ketone or aldehyde ( 207) and an ester ( 172).

ethyl acetoacetate CH3COCH2COOCH2CH3

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MASS SPECTROSCOPY

Mass Spectrum Fragments: 
The mass spectrum consists of a molecular ion at 130, an m-15 peak at 115, which is consistent with loss of a CH₃ group, an m-43 peak (loss of acylium), an m-45 peak (loss of CH₃CH₂O-), and a base peak at m-43(m/e = 43) which suggests the formation of an acylium ion (CH₃-CO). The spectrum is consistent with a molecule which can lose methyl or ethoxy radicals, or can undergo fragmentation to form the acylium radical cation.

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IR

3400-3200 cm^–1: no OH peak (too small) 3100 cm^–1: no significant peak, suggesting no unsaturated CH 2900 cm^–1: strong peak suggesting saturated CH 2200 cm^–1: no unsymmetrical triple bonds 1710 cm^–1: strong carbonyl with a second peak at 1670 cm^–1, suggesting a the possibility of two carbonyls 1600 cm^–1: no significant peaks, suggesting no carbon-carbon double bonds

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2D [1H,1H]-TOCSY

1D DEPT135





2D [1H,13C]-HSQC



2D [1H,13C]-HMBC





2D [1H,1H]-COSY


2D [1H,13C]-HMQC

 

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