Oligomerization of trichloroacetaldehyde (chloral) was carried out with the lithium salt of (1S, 2R, 4S)-(-)-borneol as the initiatior. The unimer and dimer fractions consisted of two and four diastereomers, respectively; the individual isomers were isolated from the fractions by crystallization from methanol or by high performance liquid chromatography. The X-ray single-crystal analysis showed that the major isomer in the unimer fraction is the (R)-form which has the acetal carbon in (R)-configuration. The diastereomeric ratios were determined by H-1 NMR as R/S = 57/43 for the unimers and RS/SR/RR/SS = 34/25/23/18 for the dimers. The conformations of the meso-dimers [(R,R)- and (S,S)-isomers] in the crystalline form corresponded to a half turn of the 4(1)-helix of isotactic polychloral, whereas the conformations of the racemo-dimers (the (R,S)- and (S,R)-isomers) were different from the helical structure in the crystal and in solution. The trimer fraction consisted of six of the eight possible diastereomers; among these isomers, the mm isomers (the (R,R,R)- and (S,S,S)-isomers) were highly predominant. The amount of the (R,R,R)-trimer formed was only slightly larger than that of the (S,S,S)-isomer.

Bornyl oxide initiated, acetate endcapped unimers of trifluoroacetaldehyde, trichloroacetaldehyde and tribromoacetaldehyde were prepared and their optical rotations were determined. The value of the optical rotations of the unimers was correlated to the bulk size of the trihalomethyl group and they were compared to those of the unimer of formaldehyde and bornyl acetate. The bornyloxy terminated trihaloacetaldehydes consist of 2 diastereomeric unimers. In the cases of the chloral and bromal unimers they have been isolated. One diastereomer of the trichloroacetaldehyde unimers was crystallized and its absolute configuration was established by x-ray spectroscopy.