4- Pentenal, 2,2-dimethyl

The same reaction that gave 2 4 4 trimethyl 2 pentene also yielded an isomeric alkene This second alkene produced formaldehyde and 4 4 dimethyl 2 pentanone on ozonolysis Identify this alkene... 

A telomerization reaction of isoprene can be carried out by treatment with 2-chloro-3-pentene, prepared by the addition of dry HCl to 1,3-pentadiene (67). An equimolar amount of isoprene in dichi oromethane reacts with the 2-chloro-3-pentene at 10°C with stannic chloride as catalyst. l-Chloro-3,5-dimethyl-2,6-octadiene is obtained in 80% yield by 1,4-addition. 

Dimethyl- Propene Ethane, ethylene, propane, 1- butene, 2,3-dimethylbutane, 2- methyl-4-pentene, isobutane, 1,5-hexadiene... 

In laser-impulse experiments with chlorophenyldiazirine the carbene could be observed by UV spectroscopy. On addition of defined amounts of alkene the rate of cyclopropanation was measured directly. The rate constants with various alkenes were (lO moF s ) 1-hexene, 1.3 ( )-2-pentene, 34 2-methyl-2-butene, 77 2,3-dimethyl-2-butene, 130 (80JA7576>. 

Dimethyl sultide Methyl sulfide 187 C,H,S 1-Pentene 33 CsHio... 

Methyl 2-hydroxy-2-carbomathoxy-4-haptenoate (3), A solution of dimethyl mesoxalate 2 (1.46 g, 10 mmol] and 1-pentene 2 (0 70 g, 10 mmol) in CH2CI2 was heated at 140 C lor 16 h. The solvent was reirroved and the residue distilled under reduced pressure. The fraction collected between 90 and 105°C (0 5 torr) was diluted with Et20 (20 mL), washed with water and dned The residue after evaporation of the solvent, gave on dislillation 1 55 g of 3 (62%), bp 89-90 C (0 2 torr). 

A. 2,2-Dimethyl-4-pentenal. In a SOO-mL, one-necked, round-bottomed flask which contains a magnetic stirring bar are placed 108 g (1.5 mol) of 1 sobutyraldehyde (Note 1), 58 g (1.0 mol) of ally alcohol (Note 1), 230 ml of p-cymene (Note 1), and 0.4 g (2 mnol) of p-toluenesulfonic acid nonohydrate... 

Note 1). The mixture is heated with a mantle with stirring for 32 hr under a 50-cm fractionating column packed with 5-nm glass beads and topped by a Dean-Stark trap. The reaction mixture is then distilled through the packed column. The fraction which boils at 120 -126°C is collected. The yield is 86.0-87.3 g (77-78%) of 2,2-dimethyl-4-pentenal (1) as a clear, colorless oil, n 1.4216 (Note 2). 

C—3 increases the preference for the eclipsed conformation analogous to B at the expense of A. 4,4-Dimethyl-1-pentene exists mainly in the hydrogen-eclipsed conformation. 

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