Look at the figure. On the left carbon is drawn flat with four sticks — convenient but a lie about the geometry. On the right is the truth: the four bonds splay out at ~109.5° into 3D space.
Why the topic needs this: the carbonyl group (next section) is a C=O double bond, and the whole idea of a "chiral centre" (§4) needs carbon's four different attachments in 3D.
Why the topic needs this: the two-word code is the entire naming system for monosaccharides. Once you can read "aldohexose", classification (§ parent's Section 1) is trivial.
Read it top-down: the four bonds of carbon split into "which groups?" (giving names) and "different groups?" (giving handedness). Handedness feeds the stereo-vocabulary and optical rotation; the hydroxyl+carbonyl pair feeds ring formation, which creates the anomeric carbon that powers α/β, mutarotation, and glycosidic bonds — and those, via water bookkeeping, give the final mono/di/poly classification.
How many bonds does carbon form, and in what shape? ::: Four bonds, pointing to the corners of a tetrahedron (3D, ~109.5°).
What does a single line "–" and a double line "=" between atoms mean? ::: One shared electron pair vs two shared pairs (a stronger, non-rotating bond).
What is a hydroxyl group and what is polyhydroxy? ::: –O–H attached to carbon; polyhydroxy means many –OH groups.
Difference between an aldehyde (–CHO) and a ketone (>C=O)? ::: Aldehyde C=O is at the chain end (also holds an H); ketone C=O is internal.
What does "aldohexose" tell you? ::: Aldehyde-type carbonyl + 6 carbons (e.g. glucose).
Where does carbon numbering start in glucose and why? ::: At the –CHO end (C1), so addresses like "α(1→4)" have meaning.
What makes a carbon a chiral centre? ::: It carries four different groups, so its mirror image is a distinct molecule.
Enantiomer vs diastereomer vs epimer vs anomer? ::: Mirror at every centre / differ at some centres / differ at exactly one / differ at the anomeric C1.
What does [α]D measure and what do + and − mean? ::: Specific optical rotation in degrees; + clockwise, − anticlockwise twist of polarised light.
Why is a changing rotation evidence of a chemical change? ::: Each anomer has a fixed rotation, so drift means α⇌β interconversion (mutarotation).
What is a hemiacetal and how does it make the anomeric carbon? ::: –OH adds across C=O, giving a carbon with both –OH and –OR; the old carbonyl C becomes a new chiral centre.
What is a glycosidic bond in one line? ::: The C–O–C bridge joining two sugars, formed when an anomeric –OH condenses with another –OH.
Condensation vs hydrolysis water bookkeeping? ::: Condensation loses one H₂O to form a bond; hydrolysis adds one H₂O to break it.
