Internal Rotation in n-Propyl Chloride and Bromide

Abstract

Infrared spectra of n-propyl chloride and bromide have been measured in the gaseous, liquid and solid states. The Raman measurement was also made in the liquid state. From the normal vibration calculation and by comparison with the spectra of ethylene chlorhydrin it has been concluded that in the liquid state both the trans and gauche forms are present and of these only the trans form persists in the solid state. The energy difference between the trans and the gauche forms has been determined by the absorption intensity measurement.

Specification of Molecular Chirality

“…In the anhydride (2S), C-3 is symmetric, as in the free acid, and hence receives no label. In hydroshikimic acid (26), and its diastereoisomer (27), C-1 and C-4 are asymmetric, and are labelled by Sub-rule (3). In the myoinositol ether,…”

Experimental Molecular Structure

“…The stable form in the solid state of the molecules of the types XH2C CH2X and XH2C-CH2Y is the trans form (124,131,136), except for CIH2C-CH20H with internal hydrogen bonding (149) and NC· H2C CH2· CN (150). In CI2HC-CHCI2 (130) and Br2HC-CHBr2 (144) the gauche form was found to be stable in the solid state, although the latter sub stance crystallizes as trans molecules by employing a different method of cooling (145).…”

“…The determination of the energy difference between the rotational iso mers has been continued (131,138,143,147,151). The results confirm pre vious conclusions (124).…”

Ab Initio calculations of the stabilization energies of the conformational and the structural isomers of C3H7X where X = F, Cl, and Br

“…However, some of the done experiments on the conformations of 1‐chloropropane13–15 and of 1‐bromopropane15 indicate that the G and the A conformers are approximately of the same stability in both compounds. Other experiments show that G conformer is more stable than A in both 1‐chloropropane9, 16 and 1‐bromopropane 9, 13. Consequently, the second purpose of the present work is doing ab initio investigations on the relative stabilities of the gauche conformers of 1‐fluoro‐, 1‐chloro‐, and 1‐bromopropanes.…”

“…All experimental studies done on conformations of 1‐fluoropropane indicate that G conformer is preferred over the A conformer 8–12. However, some of the done experiments on the conformations of 1‐chloropropane13–15 and of 1‐bromopropane15 indicate that the G and the A conformers are approximately of the same stability in both compounds. Other experiments show that G conformer is more stable than A in both 1‐chloropropane9, 16 and 1‐bromopropane 9, 13.…”