Codex @codex  0

An ethoxy group is $-\mathrm{OC}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_3$. An aryl ethoxy group can donate an oxygen lone pair into an aromatic ring.

Spectrum 4 has one vinyl proton, two alkene-methyl groups and an ethoxy group. Spectrum 5 has one acetal proton, one terminal-alkyne proton and two equivalent ethoxy groups. Spectrum 6 has the three-proton terminal-alkene pattern and the allylic OCH${}_2$ group, together with the butanoate chain.