Structure 3.2 Flashcards

A family of organic compounds in which successive members differ by a common structural unit (typically CH2) and share the same general formula.

A specific atom or group of atoms that gives characteristic physical and chemical properties to a compound.

Empirical = simplest whole-number ratio of atoms. Molecular = actual number of atoms. E.g. Glucose: empirical CH2O, molecular C6H12O6.

C atoms are at each vertex/end. H atoms on C are omitted (carbon always has 4 bonds). Heteroatoms (O, N, halogens) are shown explicitly.

-ol (alcohol), -al (aldehyde), -one (ketone), -oic acid (carboxylic acid).

Class = the type of compound (e.g. Alcohol, carboxylic acid). Functional group name = the actual group (e.g. Hydroxyl, carboxyl). The IB tests this distinction.

Amine has -NH2 (amino group, suffix -amine). Amide has -CONH2 (carbonyl bonded to N, amido group, suffix -amide). Completely different functional groups.

These are terminal groups - by definition they can only exist at the end of the chain. No locant is needed: write butanal, not butan-1-al.

meth- (1), eth- (2), prop- (3), but- (4), pent- (5), hex- (6).

1. Longest chain containing the group. 2. Suffix (and an or en). 3. Number from the end nearer the group. 4. Name and number branches and halogens. 5. Prefixes in alphabetical order, then punctuation.

First the suffix group (-ol, -one, -al, -oic acid), then the C=C, then all prefixes together. On a tie, the prefix first in the alphabet gets the lower number.

Before a suffix starting with a vowel: propane becomes propan-1-ol. It stays before a consonant: ethane-1,2-diol.

fluoro-, chloro-, bromo-, iodo-. Halogens are always prefixes, numbered like branches.

Alphabetically, ignoring di- and tri-: 3-ethyl-2,2-dimethylpentane (e before m).

Commas between numbers (2,3); hyphens between numbers and letters (2-methyl). No spaces: 2,3-dimethylbutane.

No. The longest chain runs through the ethyl group: 5 carbons. The correct name is 3-methylpentane.

But-2-ene. Number from either end: the C=C starts at carbon 2.

Acetone is propanone. Acetic acid is ethanoic acid.

Tertiary. The carbon bonded to Br is bonded to three other carbons.

The C=O can only be on carbon 2 of a four-carbon chain (carbon 1 would make it an aldehyde), so the name is unambiguous.

Molecules with the same molecular formula but different connectivity (arrangement of atoms).

Chain isomers (different carbon skeleton), positional isomers (FG in different position), functional group isomers (different FG entirely).

Name both using IUPAC rules. If they have the same name, they are the same molecule. Bending the chain at 90 degrees does NOT create an isomer.

BP increases with chain length - longer chain = more electrons = bigger surface area = stronger London dispersion forces.

Branching reduces the surface area for intermolecular contact, weakening London dispersion forces.

Solubility decreases because the non-polar hydrocarbon chain becomes dominant over the polar -OH group.

Classify by how many carbons are bonded to the alpha-carbon (the C bearing -OH). 1 degree = one C, 2 degree = two C, 3 degree = three C.

For amines, classify by how many carbons are bonded directly to the nitrogen atom, not the alpha-carbon.

1. Restricted rotation (C=C double bond or small ring). 2. Each carbon of the double bond must have two DIFFERENT groups attached.

No! Both carbons must have two different substituents. If one carbon has two identical groups, no cis-trans isomerism exists.

A carbon atom bonded to four different groups. Creates non-superimposable mirror images (enantiomers).

Identical physical properties (BP, solubility, density) but rotate the plane of polarised light in opposite directions. Measured by a polarimeter.

The relative molecular mass (Mr) of the compound. The [M+1] peak from C-13 abundance can estimate the number of carbon atoms.

Homonuclear diatomic molecules (N2, O2, H2) because their vibrations cause no change in dipole moment. A net dipole change is required for IR absorption.

A signal splits into (n+1) peaks where n = number of equivalent H on adjacent carbons. E.g. 3 neighbours = quartet, 2 neighbours = triplet.

The number of distinct (non-equivalent) carbon environments in the molecule.

No. The IB only requires cis and trans labels. E/Z nomenclature is not assessed.

IHD = 0.5 x (2C + 2 - H - X + N). Halogens count like H (subtract), O is ignored, N adds 1. A benzene ring = IHD of 4 (1 ring + 3 double bonds).