Interactive Learning Guide — Ionic Compounds, Balancing, Functional Groups & Organic Reactions
Ions combine until their charges cancel to zero (electrical neutrality). Think of it like balancing a scale.
| Group | Charge | Examples |
|---|---|---|
| Group 1 | +1 | Na⁺, K⁺, Li⁺ |
| Group 2 | +2 | Ca²⁺, Mg²⁺, Ba²⁺ |
| Group 13 | +3 | Al³⁺ |
| Group 16 | −2 | O²⁻, S²⁻ |
| Group 17 | −1 | F⁻, Cl⁻, Br⁻, I⁻ |
a. Ca and Cl
CaCl₂
(+2) + 2(−1) = 0 ✓
b. Mg and O
MgO
(+2) + (−2) = 0 ✓ — Equal charges always simplify to 1:1.
c. K and O
K₂O
2(+1) + (−2) = 0 ✓
d. Pb⁴⁺ and F
PbF₄
(+4) + 4(−1) = 0 ✓
Polyatomic ions are groups of atoms that travel together as one charged unit — like a team that stays together.
| Name | Formula | Charge |
|---|---|---|
| Hydroxide | OH⁻ | −1 |
| Ammonium | NH₄⁺ | +1 |
| Carbonate | CO₃²⁻ | −2 |
| Nitrate | NO₃⁻ | −1 |
| Sulfate | SO₄²⁻ | −2 |
| Sulfite | SO₃²⁻ | −2 |
| Phosphate | PO₄³⁻ | −3 |
a. Ca and hydroxide
Ca(OH)₂
b. Ammonium and Cl
NH₄Cl
c. Cu²⁺ and sulfate
CuSO₄
d. K and sulfite
K₂SO₃
No parentheses because K is a simple ion, not polyatomic.
Atoms don't appear or disappear — they just rearrange. Every atom on the left must appear on the right. You only change coefficients (big numbers in front), never subscripts.
a. NaCl(aq) + Pb(NO₃)₂(aq) → NaNO₃(aq) + PbCl₂(s)
2NaCl(aq) + Pb(NO₃)₂(aq) → 2NaNO₃(aq) + PbCl₂(s)
b. CaBr₂(aq) + Na₂CO₃(aq) → NaBr(aq) + CaCO₃(s)
CaBr₂(aq) + Na₂CO₃(aq) → 2NaBr(aq) + CaCO₃(s)
c. HCl(aq) + Ba(OH)₂(aq) → H₂O(l) + BaCl₂(aq)
2HCl(aq) + Ba(OH)₂(aq) → 2H₂O(l) + BaCl₂(aq)
d. C₃H₈(g) + O₂(g) → CO₂(g) + H₂O(l)
C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(l)
The functional group is the specific atom arrangement that controls how a molecule behaves. The carbon chain is just a handle — the functional group is where the chemistry happens.
| What You See | Functional Group |
|---|---|
| C=C in the chain | Alkene |
| −OH on a carbon (no C=O next to it) | Alcohol |
| C=O between two carbons | Ketone |
| C=O with −OH at end of chain (−COOH) | Carboxylic Acid |
| C=O − O − C (ester linkage) | Ester |
| C=O bonded to N | Amide |
| −NH₂ with no C=O nearby | Amine |
a) Chain with internal C=C double bond
Alkene
The C=C double bond is the defining feature. No oxygen, no nitrogen — just a carbon-carbon double bond.
b) Chain with −OH group
Alcohol
An −OH bonded to a carbon chain. No carbonyl (C=O) nearby, so it's an alcohol, not a carboxylic acid.
c) Chain with C=C near the end
Alkene
Same rule — a C=C double bond makes it an alkene regardless of position in the chain.
d) Chain with C=O flanked by two carbon chains
Ketone
C=O flanked by carbons on BOTH sides. No −OH on the carbonyl carbon, no N → ketone.
e) Chain ending in −C(=O)OH
Carboxylic Acid
C=O PLUS an −OH on the same carbon = −COOH = carboxylic acid. The most oxidized single-carbon functional group.
f) Chain with C=O bonded to −NH₂
Amide
C=O bonded to nitrogen = amide. Key distinction: amides have C=O next to N. Amines do NOT have a C=O.
g) Cyclopentane ring with −OH
Alcohol
−OH on a ring carbon = cyclic alcohol (cyclopentanol). Ring or chain doesn't matter — −OH on carbon = alcohol.
h) Cyclohexane ring with −NH₂
Amine
−NH₂ on a carbon with NO carbonyl nearby = amine. If there were a C=O next to the N, it would be an amide.
Hydrogenation adds H₂ across a C=C double bond using a Pt catalyst. The double bond breaks and each carbon grabs one H.
a) Hex-2-ene + H₂ / Pt →
Product: Hexane
The double bond disappears. The 6-carbon chain stays intact, now fully saturated.
b) Cyclohexene + H₂ / Pt →
Product: Cyclohexane
The double bond in the ring disappears. Cyclohexene → cyclohexane.
c) 3-Methyl-2-pentene + H₂ / Pt →
Product: 3-Methylpentane
The double bond saturates. The methyl branch stays put. Skeleton unchanged — just no more double bond.
Hydration adds water (H₂O) across a C=C double bond using an acid catalyst (H⁺). The −OH attaches to one carbon, H to the other.
d) Hex-2-ene + H₂O / H⁺ →
Products: 2-Hexanol or 3-Hexanol
C2 and C3 are similarly substituted, so OH can attach to either, giving a mixture.
e) Cyclohexene + H₂O / H⁺ →
Product: Cyclohexanol
Water adds across the ring's double bond. Both carbons equivalent by symmetry.
f) 3-Methyl-1-pentene + H₂O / H⁺ →
Product: 3-Methyl-2-pentanol
Markovnikov: OH goes to C2 (the more substituted carbon of the C1=C2 double bond).
Carboxylic acids react with alcohols to form esters, and with amines to form amides. Both release water — condensation reactions.
a) Butanoic acid + Propanol →
Propyl Butanoate + H₂O
The −OH from the acid and H from the alcohol leave as water. The fragments join through a new C−O ester bond.
b) Acetic acid + 1-Butanol →
Butyl Acetate + H₂O
Acetic acid (2C) + butanol (4C) → butyl acetate. The alcohol-derived part (butyl) goes first in the name.
c) 3-Methylbutanoic acid + Cyclopentanol →
Cyclopentyl 3-Methylbutanoate + H₂O
Cyclopentyl (from the alcohol) + 3-methylbutanoate (from the acid).
d) Butanoic acid + Propylamine →
N-Propylbutanamide + H₂O
Acid + amine (not alcohol) → amide (−CONH−). The N- prefix in the name indicates the propyl group is on nitrogen.
Hydrolysis is the REVERSE of ester/amide formation. Water BREAKS the bond apart, regenerating the original acid and alcohol (or amine).
a) Ethyl butanoate + H₂O →
Butanoic Acid + Ethanol
Break the ester C−O. The 4C side gets −OH → butanoic acid. The 2C side gets H → ethanol.
b) Isobutyl acetate + H₂O →
Acetic Acid + 2-Methyl-1-propanol (Isobutanol)
2C acid side → acetic acid. Branched 4C alcohol side → isobutanol (2-methyl-1-propanol).
c) N-Ethylbutanamide + H₂O →
Butanoic Acid + Ethylamine
Break the amide C−N. Carbonyl side gets −OH → butanoic acid. N side gets H → ethylamine.
d) N-(2-Methylpropyl)acetamide + H₂O →
Acetic Acid + Isobutylamine (2-Methylpropanamine)
2C acid → acetic acid. Branched amine → isobutylamine (2-methylpropanamine).