Pentines

Pentines
Surname	Pent-1-in	Pent-2-in	3-methylbut-1-yne
other names	Propyl acetylene	1-methyl-2-ethylacetylene	Isopropyl acetylene, isopentine
Structural formula
CAS number	627-19-0	627-21-4	598-23-2
PubChem	12309	12310	69019
Molecular formula	C 5 H 8
Molar mass	68.12 g mol −1
Physical state	liquid
Brief description	colorless liquid
Melting point	−106 ° C	−109 ° C	−90 ° C
boiling point	39-41 ° C	55-57 ° C	29.5 ° C
density	0.69 g cm −3	0.71 g cm −3	0.666 g cm −3 (20 ° C)
solubility	1.05 g l −1 in water	insoluble in water	?
GHS labeling	danger	danger	danger
H and P phrases	225	225-315-319-335	224-315-319-335
	no EUH phrases	no EUH phrases	no EUH phrases
	210-223-403 + 235	210-302 + 352-304 + 340 305 + 351 + 338-403 + 235	210-240-243-261-280 302 + 352 305 + 351 + 338-403 + 235

In chemistry, the pentynes form a group of unsaturated aliphatic hydrocarbons with the general empirical formula C ₅ H ₈ and a C≡C triple bond . They are therefore one of the alkynes .

There are three isomers :

• 1-pentin
• 2-pentin
• 3-methyl-1-butyne

All three isomers are volatile, flammable liquids under normal conditions and almost insoluble in water. The isomers are very reactive due to their C≡C triple bond like most alkynes and can, for. B. polymerize easily or enter into addition reactions .

Manufacture and extraction

In the preparation of the pentynes, one can start from the corresponding alkene compounds, which are first converted into the corresponding vicinal dibromides by addition of bromine . A dehydrohalogenation under basic conditions leads to the corresponding Pentinen. The synthesis of 1-pentyne is based on 1-pentene. The intermediate dibromide is dehydrohalogenated in the presence of potassium carbonate at high temperatures. 2-pentyne is produced in a similar manner, where the dehydrohalogenation takes place in alcoholic potassium hydroxide solution. The synthesis of 3-methyl-1-butyne goes from 3-methyl-1-butene from which first at -60 ° C brominated is. The resulting dibromide is dehydrohalogenated in liquid ammonia using sodium amide.

Individual evidence

1. ↑ ^{a b c d e} Data sheet 1-Pentin (PDF) from Merck , accessed on February 21, 2010.
2. ↑ ^{a b c d e} Data sheet 2-Pentin (PDF) from Merck , accessed on February 21, 2010.
3. ↑ ^{a b c} H. N. Miller, KW Greenlee, JM Derfer, CE Boord: "Mono- and Di-Alkylacetylenes from Vicinal Dihalides and Sodium Amide in Liquid Ammonia", in: J. Org. Chem. , 1954 , 19 , p. 1882 -1888 ( doi : 10.1021 / jo01377a003 ).
4. ↑ ^{a b c} 3-Methyl-1-butyne data sheet from Acros, accessed September 30, 2012.
5. ^ HH Guest: "Rearrangements of the Triple Bond", in: J. Am. Chem. Soc. , 1928 , 50 , pp. 1744-1746 ( doi : 10.1021 / ja01393a036 ).
6. ↑ ML Sherrill, ES Matlack: “Additional Data on the cis and trans Isomers of Pentene-2”, in: J. Am. Chem. Soc. , 1937 , 59 , pp. 2134-2138 ( doi : 10.1021 / ja01290a014 ).

Web links

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