The chlorination of poly(vinyl chloride) (PVC) was investigated by using deuterated polymeric models of PVC, viz., α‐deuterated PVC (α‐d‐PVC) and β,β‐dideuterated PVC (β,β‐d2‐PVC). The chlorinated samples of PVC, α‐d‐PVC, and β,β‐d2‐PVC were examined by combining infrared (IR), 1H‐NMR, 13C‐NMR, and mass spectroscopy. The results obtained were used in a study of the reaction mechanism of PVC chlorination. The selectivity of chlorination and the extent of the substitution and elimination‐addition mechanism of chlorination are discussed with respect to the degree of chlorination and chlorination conditions.

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2β-Methyl-1α-hydroxy (XV) and two isomeric 2-methyl-1-oxo derivatives (XVI and XVII) of 19β,28-epoxy-18α-oleanane were prepared from 19β,28-epoxy-2-methyl-18α-olean-1-en-3-one (XI) via 3β-chloro derivative XIII and unsaturated 1α-hydroxy derivative XIV. Allylic oxidation of 2-methyl-2-ene VI was studied as an alternative approach to compound XIV. Oxidation with selenium dioxide led to diol VII, aldehyde VIII and alcohol IV, oxidation with tert-butyl chromate gave epoxy ketone X. According to 1H NMR and CD data, ring A in the 2β-methyl derivatives XV and XVI exists in a boat conformation. The 2α-methyl ketone XVII (chair form) is more stable than its 2β-epimer XVI (boat form): only 9 ± 3% of XVI exists at equilibrium. Conformation of ring A in the unsubstituted 1-ketone I and differences in stability of the boat form in 1,2- and 2,3-disubstituted triterpenoids are discussed.

2-Methyl-3-hydroxy derivatives X, XIII, XV, XVI and 2-methyl-3-oxo derivatives III, VIII and IX of 19β,28-epoxy-18α-oleanane were prepared from ketones I and XVII. From spectral data it was deduced that compounds III, VIII and XV containing a 2β-methyl group have their A ring in boat conformation. Both isomeric 2-methyl-3-oxo derivatives VIII and IX are approximately equally stable; 52 ± 4% of the 2β-isomer VII were found in their equilibrium mixture.

Chemical shifts of signals due to methyl groups in position 10β (in CDCl3) and 4α and 4β (in C6D6) in 1H NMR spectra of pentacyclic triterpene 3-oxo derivatives (V, VIII, IX, and XII) are suitable for estimation of chair-boat equilibrium in the ring A. Benzene and lanthanide induced shifts of 4α and 4β-methyl protons were also used for this purpose. The results obtained with 2α-methyl-3-ketones (III, X) and 2β-methyl-3-ketones (IV, XI) as the respective chair and boat models agree well with those derived from other physical data (about 40% boat). The same methods were applied to 4,4-dimethylsteroid 3-ketones XV-XVII.