Context :

Aims : To reveal the morphology , chemical composition , kinematics and to establish the main processes prevalent in the gas at the foot points of the giant molecular loops ( GMLs ) in the Galactic center region

Methods : Using the 22-m Mopra telescope , we mapped the M -3.8 + 0.9 molecular cloud , placed at the foot points of a giant molecular loop , in 3-mm range molecular lines .
To derive the molecular hydrogen column density , we also observed the ^ { 13 } CO ( 2 - 1 ) line at 1 mm using the 12-m APEX telescope .
From the 3 mm observations 12 molecular species were detected , namely HCO ^ { + } , HCN , H ^ { 13 } CN , HNC , SiO , CS , CH _ { 3 } OH , N _ { 2 } H ^ { + } , SO , HNCO , OCS , and HC _ { 3 } N .

Results : Maps revealing the morphology and kinematics of the M -3.8 + 0.9 molecular cloud in different molecules are presented .
We identified six main molecular complexes .
We derive fractional abundances in 11 selected positions of the different molecules assuming local thermodynamical equilibrium .

Conclusions : Most of the fractional abundances derived for the M -3.8 + 0.9 molecular cloud are very similar over the whole cloud .
However , the fractional abundances of some molecules show significant difference with respect to those measured in the central molecular zone ( CMZ ) .
The abundances of the shock tracer SiO are very similar between the GMLs and the CMZ .
The methanol emission is the most abundant specie in the GMLs .
This indicates that the gas is likely affected by moderate \sim 30 km s ^ { -1 } or even high velocity ( 50 km s ^ { -1 } ) shocks , consistent with the line profile observed toward one of the studied position .
The origin of the shocks is likely related to the flow of the gas throughout the GMLs towards the foot points .