2-甲基-3-丁基三氟乙酸酯 | 691-75-8

• 分子结构分类: 有机化合物 - 有机酸及其衍生物 - 羧酸及其衍生物
• 中文名称: 2-甲基-3-丁基三氟乙酸酯
• 英文名称: 3-methyl-2-butyl trifluoroacetate
• 英文别名: 1,2-Dimethylpropyl trifluoroacetate；3-methylbutan-2-yl 2,2,2-trifluoroacetate
• CAS: 691-75-8
• 化学式: C₇H₁₁F₃O₂
• 分子量: 184.158
• InChiKey: IHMOIZUAENUCFQ-UHFFFAOYSA-N

计算性质

• 辛醇/水分配系数(LogP)：
  3
• 重原子数：
  12
• 可旋转键数：
  3
• 环数：
  0.0
• sp3杂化的碳原子比例：
  0.86
• 拓扑面积：
  26.3
• 氢给体数：
  0
• 氢受体数：
  5

反应信息

• 作为产物：
  描述：

  3-甲基-2-丁醇 、 三氟乙酸酐 在 吡啶 作用下， 生成 2-甲基-3-丁基三氟乙酸酯
  参考文献：
  名称：

  Fragmentation processes of methylbutyl trifluoroacetates studied by tandem quadrupole mass spectrometry and isotope labeling

  摘要：

  AbstractThe fragmentation patterns of 3‐methyl‐2‐butyl trifluoroacetate and 2‐methyl‐2‐butyl trifluoroacetate were investigated by GC/MS/MS, with electron impact and collision‐induced dissociation, on regular and isotope‐labeled (deuterium and 18O) esters. The atoms found in various fragments could be traced back to specific positions in the parent molecules. In this way, molecular rearrangements potentially occurring during the formation of esters by trifluoroacetolysis of 3‐methyl‐2‐butyl p‐toluenesulfonate or trifluoroacetic acid addition to various 2‐methylbutenes could be shown. Rearrangements also occurred during the fragmentation, particularly during the expulsion of the small fragments CO, C2H4 and F2CO. For the decompositions of oxygen‐containing ions these rearrangements were highly specific. By contrast, alkyl cations lead to fragments that are fully scrambled (statistical label distribution). Alkene radical cations ([CnH2n]+ ˙) fragment to daughter ions that are extensively, but less than statistically scrambled. Hydrogen scrambling may also occur in fluoroalkyl cation fragments.

  DOI：

  10.1002/oms.1210240906

文献信息

• Secondary and tertiary 2-methylbutyl cations. 1. Trifluoroacetolysis of 3-methyl-2-butyl tosylate
  作者：Dan Farcasiu、Gaye Marino、J. Milton Harris、Bruce A. Hovanes、Chang S. Hsu

  DOI：10.1021/jo00080a025

  日期：1994.1

  Trifluoroacetolysis rates for 3-methyl-2-butyl tosylate (4) and kinetic isotope effects st C(1) (k(H)/k(D) = 1.083 per H atom), C(2) (k(H)/k(D) = 1.10), and C(3) (k(H)/k(D) = 1.32) were determined. The products are 2-methyl-2-butyl trifluoroacetate (5, 98.5%) and 3-methyl-2-butyl trifluoroacetate (6, 1.5%). GC-MS analysis of products from labeled tosylates 4-1-d(3) and 4-2-d showed that 42% of the apparently unrearranged 6 had a methyl group shifted from the original C(3) to the original C(2), whereas 3.6% methyl shift occurred in 5. The results do not substantiate a k(s)-k(Delta) competition mechanism. Instead, two carbocations, the tertiary 2-methyl-2-butyl (1) and the nominally secondary 3-methyl-2-butyl (2) intervene. The intimate structure of 2 is not established, but a symmetrical, methyl-bridged ion (3) does not agree with the results. A high beta isotope effect does not require hydrogen assistance to ionization; ionization concerted with (assisted by) hydrogen migration is unimportant in formation of 1 (and 5) from 4. Instead, the reaction involves reversible formation of an intimate ion pair with subsequent rate-determining H shift (which for 2.OTs- is in competition with Me shift and ca. 25% elimination) followed by solvent capture. Methyl migration in 2 may occur in the solvent-separated ion pair; alternatively, methyl or hydrogen migration is conformationally determined. At least 9% of 1 is formed from 2 which has undergone methyl shift. Nucleophilic attack an 4 appears important only in strongly nucleophilic media like aqueous ethanol. The claim that nucleophilic solvent assistance is significant in solvolysis of other secondary alkyl substrates in TFA or 97% hexafluoro-2-propanol is evaluated. Such a conclusion cannot be accepted on the basis of rate correlations alone, (i.e without product studies to support it). The implications of our results for the trifluoroacetolysis of 2-butyl tosylate are briefly discussed.
• Secondary and tertiary 2-methylbutyl cations. 2. Addition of trifluoroacetic acid to methylbutene
  作者：Dan Farcasiu、Gaye Marino、Chang S. Hsu

  DOI：10.1021/jo00080a026

  日期：1994.1

  The reaction of 8-methyl-1-butene (4), 2-methyl-1-butene (5), and 2-methyl-2-butene (6) in trifluoroacetic acid (TFA), neat or buffered with potassium trifluoroacetate, and in 74:26 TFA-MeCN was studied. Alkenes 5 and 6, which form a tertiary carbocation (2) upon hydronation, react 6.6 x 10(4) and 5.8 X 10(4) times faster than 4 (TFA-MeCN, 25 degrees C). The rates in TFA-d gave KIEs of 6.8 (4, 26.5 degrees C), ca. 5 (5, -18 degrees C), and 3.9 (6, -18 degrees C). The esters 3-methyl-2-butyl trifluoroacetate (7) and 2-methyl-2-butyl trifluoroacetate (8) are formed from 4 in the same ratio in TFA and in TFA-d (ca. 53:47),thus proving that 4 reacts entirely by a carbocationic mechanism, with no measurable contribution from a molecular addition. In the presence of p-toluenesulfonic acid the reaction of 4 at 0 degrees C forms significant amounts of 3-methyl-2-butyl tosylate (3), and the final ratio of 7:8 was close to that observed in the solvolysis of 3. The different product distributions in solvolyses and alkene hydronations observed before are brought about most probably by the different anions present in the tight ion pairs rather than by differences in the nature of the intermediate carbocations. The reaction in TFA-d showed that the 3-methyl-2-butyl cation (1) undergoes methyl shift to an extent (32%) smaller than in the solvolysis of the tosylate 3 before being trapped by the solvent. Extensive H/D exchange between the solvent and ester 8 prevented us from ascertaining whether skeletal rearrangement had occurred in the latter as well. Formation of the 2-methyl-2-butyl cation (2) from 5 and 6 is reversible, leading to partial isomerization of 5 to 6 in the initial stages of the reaction. Therefore the quoted rate ratios of 5 to 6 to 4 are minimum values. Hydron loss from the ethyl group of 2 is 9.3 +/- 1.8 faster than hydron loss from a methyl group. In 74:26 TFA-MeCN, cation 2 is trapped by the two solvents in a 12.6:1 ratio at 25 degrees C.