2- Butyne boiling point

Some 3-amino-1-butynes have been reported to rearrange in the vapor phase to the isomeric 2-amino-1,3-butadienes or when heated from 10° to 30°C above their boiling point [81] (Eq. 26). Similarly, l,4-bis(dialkylamino)-... 

Butynediol (2-butyne-l,4-diol melting point 58°C, boiling point 248°C, density 1.114, flash point 152°C) is a stable crystalline solid but violent reactions can take place in the presence of certain contaminants, particularly at elevated temperatures. In the presence of certain heavy-metal salts, such as mercuric chloride, dry butynediol can decompose violently. Heating with strongly alkaline materials should be avoided. 

To compare the properties of alkanes, alkenes, and alkynes, you will be working with compounds that have the same number of carbon atoms. First, you will construct and compare butane, trans-2-butene, 2-butyne, and cyclobutane. You will use a graph to compare the boiling points of each compound. Next, you will use what you have just observed to predict the relative boiling points of pentane, trans-2-pentene, 2-pentyne, and cyclopentane. You will construct and compare these structures and graph their boiling points. 

At room temperature, the first three members of the series (ethyne, propyne and butyne) are gases, the others are liquids. Branching, as in the other hydrocarbons, decreases the boiling point. 

The physical properties of alkynes (Table 9-1) are similar to those of alkanes and alkenes of similar molecular weights. Alkynes are relatively nonpolar and nearly insoluble in water. They are quite soluble in most organic solvents, including acetone, ether, methylene chloride, chloroform, and alcohols. Many alkynes have characteristic, mildly offensive odors. Acetylene, propyne, and the butynes are gases at room temperature, just like the coitesponding alkanes and alkenes. In fact, the boiling points of alkynes are nearly the same as those of alkanes and alkenes with similar carbon skeletons. 

In the experiment that follows, the hydration of a terminal alkyne is illustrated by the conversion of 2-methyl-3-butyn-2-ol (3) to 3-hydroxy-3-methyl-2-butanone (4), as shown in Equation 11.13. The presence of a hydroxyl group in 3 has little effect on the chemical properties of the carbontriple bond. Rather, the main effect of the polar hydroxyl group is on the physical properties of the molecule, with the boiling point of 3 being considerably higher than those of other acetylenic hydrocarbons having the same molecular weight. 

There are two possible isomers of butyne, shown below. They differ by the position of the multiple bond. The melting and boiling points are given below the structures to... 

Alkynes have boiling points very similar to those of the corresponding alkenes and alkanes. Ethyne is nnnsnal in that it has no boiling point at atmospheric pressnre rather, it sublimes at 84°C. Propyne (b.p. -23.2°C) and 1-butyne (b.p. 8.1°C) are gases, whereas 2-butyne is barely a Uquid (b.p. 27°C) at room temperature. The medium-sized alkynes are distillable liquids. 

The boiling points of 3,3-dimethyl-l-butyne and 1-hexyne are 39.5 °C and 71.3 °C, respectively. Explain why the values are so different for these two isomers. 

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