State the name of the functional group forming part of the ring structure of each monosaccharide unit.

Classify, giving your reason, the hexose (six-membered) ring of sucrose as an α or β isomer.

Sketch the cyclic structures of the two monosaccharides which combine to form sucrose.

acetal
OR
ether  [✔]

Note: Accept “glycosidic bond/linkage” but not “glucosidic”.

Do not accept “hemiacetal”.

α-isomer AND hydroxyl group on carbon 1 and –CH₂OH are trans
OR
α-isomer AND hydroxyl group on carbon 1 is below plane of ring
OR
α-isomer AND glycosidic linkage between rings is below plane of ring  [✔]

Note: Accept “ether linkage” for M3.

  [✔]

[✔]

This was reasonably answered although there were some candidates who stated ester or hemiacetal, which is incorrect.

This part was very poorly answered. Majority of the candidates had no idea about the reason whether the six-membered ring was an alpha or beta isomer.

This question was poorly answered. Many candidates lost marks due to sloppy drawing and incorrect bond linkages. Some candidates did not separate the two monosaccharides as instructed.