Orgo & IM Forces

Question 1

What is the H-C-H bond angle in methane (CH₄)?

Answer 1

109.5°

Question 2

What is the bond strength of a C–H bond in methane?

Answer 2

439 kJ/mol

Question 3

What are the Van der Waals radii of carbon and hydrogen atoms?

Answer 3

C = 1.7 Å, H = 1.2 Å

Question 4

What is the melting and boiling point of methane?

Answer 4

mp: -182°C, bp: -160°C

Question 5

What is the C–C bond length and strength in ethane (C₂H₆)?

Answer 5

Length = 1.54 Å, strength = 377 kJ/mol

Question 6

What is the general formula of alkanes?

Answer 6

CₙH₂ₙ₊₂

Question 7

Name a common use of methane, propane, and butane.

Answer 7

Methane: natural gas; Propane: heating/cooking; Butane: lighters

Question 8

What carbon chain length range corresponds to petrol?

Answer 8

C5 to C12

Question 9

What is the main difference between staggered and eclipsed conformers in Newman projections?

Answer 9

Staggered conformers have atoms as far apart and are more stable; eclipsed have higher energy and torsional strain.

Question 10

What is the energy barrier for rotation between staggered and eclipsed ethane conformers?

Answer 10

About 12 kJ/mol

Question 11

What are the two types of staggered conformers in butane?

Answer 11

Anti (most stable, CH₃ groups 180° apart) and Gauche (less stable, CH₃ groups 60° apart)

Question 12

Which butane conformer is least stable and why?

Answer 12

Synperiplanar eclipsed; due to steric and torsional strain from close CH₃ groups

Question 13

What hybridisation do carbon atoms in alkanes exhibit?

Answer 13

sp³

Question 14

What is Hückel’s rule used to determine?

Answer 14

Whether a compound is aromatic

Question 15

What hybridisation do carbon atoms in alkynes have?

Answer 15

sp

Question 16

What type of bonds constitute a triple bond in alkynes?

Answer 16

One sigma (σ) bond and two pi (π) bonds

Question 17

What is the bond length and strength of the C≡C bond in ethyne?

Answer 17

Length: 1.20 Å; Strength: 965 kJ/mol

Question 18

What are primary, secondary, tertiary, and quaternary carbons?

Answer 18

Carbons bonded to 1, 2, 3, or 4 other carbons, respectively

Question 19

Name three functional groups covered in this course.

Answer 19

Examples: alcohols, ketones, amines

Question 20

What is the order of priority for functional groups in IUPAC naming?

Answer 20

1) Carboxylic acids, 2) Esters, 3) Amides, 4) Nitriles, 5) Aldehydes, 6) Ketones 7) alcohols 8) amines 9) ethers

Question 21

How is a carbonyl group represented in valence bond theory?

Answer 21

One σ bond (sp²-sp²) and one π bond (p-p) polarized toward oxygen

Question 22

What causes a covalent bond to be polar?

Answer 22

Difference in electronegativity (ΔEN) between bonded atoms

Question 23

What is a dipole moment and what unit is it measured in?

Answer 23

Measure of molecular polarity; measured in Debye (D)

Question 24

What are the three main types of intermolecular forces?

Answer 24

Dispersion forces, dipole-dipole interactions, hydrogen bonding

Question 25

What defines a hydrogen bond?

Answer 25

Attraction between a hydrogen atom bonded to N, O, or F and a lone pair on N, O, or F

Question 26

What is conformational isomerism?

Answer 26

Isomers differing by rotation around a single C–C σ bond

Question 27

Who won the Nobel Prize for the concept of conformation?

Answer 27

Derek Barton & Odd Hassel (1969)

Question 28

What is the IUPAC rule for naming alkanes?

Answer 28

Find the longest carbon chain, number it to give substituents lowest numbers, name and order substituents.

Question 29

How do you draw alkanes in skeletal form?

Answer 29

Use lines for bonds and vertices for carbon atoms; omit H atoms for simplicity.

Question 30

What are saturated hydrocarbons?

Answer 30

Alkanes; hydrocarbons with only single C-C bonds.

Question 31

What are some uses of saturated hydrocarbons?

Answer 31

Fuels (e.g. methane), lubricants, solvents, and starting materials for chemical synthesis.

Question 32

What is the C-H bond length?

Answer 32

1.09A