Researcher

Evan Curtin

Objective

To determine the melting point of cyclobutylamine

Procedure

Slowly added dry ice to a 250 mL beaker filled roughly half way with acetone. This was repeated until the dry ice remained in solid form for several minutes at a time, indicating temperatures of -78C. The sample was wrapped in parafilm, leaving some extra parafilm to be used as a handle. The sample was kept in the bath for just under four hours, while adding dry ice as necessary to maintain the low temperature.

Results

Cyclobutylamine did not solidify after 4h at -78C.

Discussion

There is only one previously recorded melting point for cyclobutylamine in the open melting point database at this time. The graph below shows the experimental melting points and predicted melting points as a function of the number of carbons in cyclic amines. The value of -4C for cyclobutylamine appears to disagree with the trend and the predictions of the melting point model. For this reason, the compound was chosen for investigation.
external image mptemp10.jpg
Source: http://usefulchem.blogspot.com/2011/07/rapid-analysis-of-melting-point-trends.html

Upon cooling for multiple hours at -78C, the sample did not ever become solid. It did become viscous, however. The lack of freezing after prolonged exposure to this low of a temperature seems to support both the melting point model and the apparent trend of cyclic amines, at least more so than the previous value of -4C. The exact melting point was not determined in this experiment, and it is possible that it is below the range of a dry ice/acetone bath. It is important to remember that 4-benzytoluene did not freeze after a few days, but rather took weeks to freeze in Exp266. The possibility of an even lower melting point in this case could make measuring that melting point a difficult task.
[Good analysis JCB]
[A logical next experiment would be to freeze in liquid nitrogen then let warm in dry ice/acetone at -78C JCB]

Conclusion

The exact melting point of cyclobutylamine was not determined but is possibly below -78C, however there seems to be yet another reason to doubt the previous value of -4C.

Log

2011-08-10

16:40 - Made dry ice/acetone bath
16:44 - Removed cyclobutylamine (1g) from refrigerator (-4C), wrapped container in parafilm. Added to dry ice/acetone bath.
16:58 - Sample is still liquid, but is more viscous.
17:36 - Sample is unchanged.
17:54 - Sample is still a viscous liquid.
20:36 - Sample remains a viscous liquid. Removed from bath and put in refrigerator. (During the dry ice/acetone bath, dry ice was added as needed to ensure that there was always solid dry ice in the bath.)