Knowledge Bank

Low resolution microwave spectra of butyryl fluoride, chloride, and bromide display band series from syn-anti $(\tau 1(OCCC)=0\circ ,\tau 2(CCCC)=180\circ )$ and syn-gauche $(\tau 1(OCCC)=0\circ ,\tau 2(CCCC)=70\circ )$ conformers. The syn-anti forms are characterized by B + C values of 3359(5); 2446(3)/2399(3), $(35Cl/37Cl)$ and $1720(3)/1705(3),(79Br/81Br)$ MHz for the fluoride, chloride, and bromide, respectively. The syn-gauche forms are characterized by B +C values of $4114(7);2804(3)/2746(5),(35Cl/37Cl)$ and 1899(3)/1883(3), $(79Br/81Br)$ for the fluoride, chloride, and bromide, respectively. Butyryl fluoride also displays band series from a skew-anti $(\tau 1(OCCC)=120\circ ,\tau 2(CCCC)=180\circ )$ conformer characterized by a B + C value of 3523(6) MHz. In all cases the syn-anti and syn-gauche conformers are of approximately equal stability. The skew-anti conformer of butyryl fluoride is marginally lees stable than the syn-anti and syn-gauche forms.""