2- Methylpent-2-enal

Several NaOH-treated ionic liquids for self- and cross-aldol condensation reactions of propanal provide an interesting example illustrating improved product selectivity in a system in which competing reactions take place (109). In the self-aldol condensation reaction of propanal, 2-methylpent-2-enal is formed. The reaction progresses through an aldol intermediate and produces the unsaturated aldehyde. The NaOH-treated ionic liquid [BDMIM]PF gave the highest product... 

When propionaldehyde is warmed with sodium hydroxide, one of the products is 2-methylpent-2-enal. Propose a mechanism for this reaction. 

C.35) 2-Pentenal, 2-methyl-, 2-methylpent-2-enal, 2-methyl-2-pentenoic aldehyde, a-methyl-3-ethylacrolein 623-36-9] FEMA 3194 ( )- [14250-96-5] (Z)-, [16958-22-8]... 

In 2015, Behr s group investigated the hydroformylation of 1,3-pentadiene (piperylene) (Scheme 4.12) [79]. With a Xantphos-based rhodium catalyst, mainly /Z-2-methylpent-2-enal was obtained. By running the reaction in... 

A mixture of propionaldehyde, formaldehyde, and Ng as carrier passed at 300° over KOH-on-clay 2-methylacrolein. Y 59%. - Similarly with propionaldehyde only over KOH-on-pumice -> 2-methylpent-2-enal. Y 57%. F. catalysts s. F. Wolf, A. Losse, and J. Miidce, J. pr. 313, 145 (1971). 

By far the most important compounds of this type are the a,/ -unsaturated aldehydes and ketones, of which the simplest general representation is (8) and (9) respectively. Branching may be present at either or both of the a- or p- positions as for example in 2-ethylhex-2-enal (10) and 4-methylpent-3-en-2-one (11). Compounds where the carbon-carbon double bond is terminal are acraldehyde [(8), R=H], and the alkyl (or aryl) vinyl ketones [(9), R = H, R = alkyl, aryl etc.]. 

There is no direct experimental evidence for this complex decomposition and it may well occur by several steps [107]. However, substantial yields of unsaturated carbonyl compounds are formed particularly at high pressures [78] under initial reaction conditions where cool flames propagate. For example, the cool-flame oxidation of 2-methylpentane at 525 °C and 19.7 atm in a rapid compression machine [78] yields no less than 14 unsaturated carbonyl compounds viz acrolein, methacrolein, but-l-en-3-one, pent-2-enal, pent-l-en-3-one, pent-l-en-4-one, trans-pent-2-en-4r one, 2-methylbut-l-en-3-one, 2-methylpent-l-en-3-one, 4-methylpent-l-en-3-one, 2-methylpent-l-en-4-one, 2-methylpent-2-en-4-one, 2-methyl-pent-2-enal and 4-methylpent-2-enal. Spectroscopic studies of the preflame reactions [78] have shown that the unsaturated ketones account for ca. 90 % of the absorption which, occurs at 2600 A. At lower initial temperatures and pressures acrolein and crotonaldehyde are formed from n-pentane [69, 70] and n-heptane [82], and acrolein is also formed from isobutane [68]. 

Methylquinoline is formed from aniline and but-2-enal (crotonaldehyde), whereas 4-methylquino-line is obtained from methyl vinyl ketone the 1,2-dihydroquinoline 85 is the end product when 4-methylpent-3-en-2-one (mesityl oxide), a terminally disubstituted enone, is used. 

---