  We report high angular resolution observations, made with the Atacama Large
Millimeter Array in band 6, of high excitation molecular lines of $\rm CH_3CN$
and $\rm SO_2$ and of the H29$\alpha$ radio recombination line towards the
G345.0061+01.794 B HC H II region, in order to investigate the physical and
kinematical characteristics of its surroundings. Emission was detected in all
observed components of the J=14$\rightarrow$13 rotational ladder of $\rm
CH_3CN$ and in the $30_{4,26}-30_{3,27}$ and $32_{4,28}-32_{3,29}$ lines of
$\rm SO_2$. The peak of the velocity integrated molecular emission is located
$\sim$0$\,.\!\!^{\prime\prime}$4 northwest of the peak of the continuum
emission. The first-order moment images and channel maps show a velocity
gradient, of 1.1 km s$^{-1}$ arcsec$^{-1}$, across the source, and a
distinctive spot of blueshifted emission towards the peak of the zero-order
moment. The rotational temperature is found to decrease from 252$\pm24$ Kelvin
at the peak position to 166$\pm16$ Kelvin at its edge, indicating that our
molecular observations are probing a hot molecular core that is internally
excited. The emission in the H29$\alpha$ line arises from a region of
0$\,.\!\!^{\prime\prime}$65 in size, where its peak coincides with that of the
dust continuum. We model the kinematical characteristics of the "central blue
spot" feature as due to infalling motions, suggesting a central mass of
172.8$\pm8.8 M_{\odot}$. Our observations indicate that this HC H II region is
surrounded by a compact structure of hot molecular gas, which is rotating and
infalling toward a central mass, that is most likely confining the ionized
region. The observed scenario is reminiscent of a "butterfly pattern" with an
approximately edge-on torus and ionized gas roughly parallel to its rotation
axis.
