  At the first Galactic quadrant, at l=33.134, b=-0.091, an extended
photodissociation region generated by an HII region complex lies. This region
is related to abundant molecular gas, and particularly, a hot molecular core,
known as G33.133-mm3, appears embedded in a molecular clump. Using data from
the James Clerk Maxwell Telescope with an angular resolution of about 15", we
studied the 13CO/C18O abundance ratio towards the mentioned molecular clump and
its relation with the ultraviolet radiation. At smaller spatial scales, using
data from the Atacama Large Millimeter Array (angular resolution about
0.7\arcsec), the hot molecular core G33.133-mm3, that has a size of about 2600
au, and is an appropriate site to form stars, was characterized. In particular,
some points about its chemistry are mentioned based on the emission of the
cyanide or nitrile radical (CN) and others more complex molecules, such as
CH3OH, CH3CN, CH3OCHO, and CH3CCH.
