Shapes and Structures 1 - Basic Stuff

Question 1

What does a bold bond mean?

Answer 1

Out of plane of the paper

Question 2

What does a hashed bond mean?

Answer 2

Back into the plane of the paper

Question 3

What does a dashed bond mean?

Answer 3

A partial bond

Question 4

In skeletal, how are triple bonds done?

Answer 4

Linear

Question 5

Which model of benzene is preferable and why?

Answer 5

3 double bond one over circle benzene

Better for curly arrow mechanisms

Question 6

What is Me short for?

Answer 6

Methyl

-CH3

Question 7

What is Et short for?

Answer 7

Ethyl

-CH2CH3

Question 8

What is nPr short for?

Answer 8

Normal propyl

-CH2CH2CH3

Question 9

What is iPr short for?

Answer 9

Isopropyl

-CH(CH3)2

Question 10

What is nBu short for?

Answer 10

Normal butyl

-CH2CH2CH2CH3

Question 11

What is tBu short for?

Answer 11

Tertiary butyl

-C(CH3)3

Question 12

What is Ac short for?

Answer 12

Acetyl

CH3CO-

Question 13

What is Ph short for?

Answer 13

Phenyl

-C6H5

Question 14

What is R short for?

Answer 14

Any alkyl group

Question 15

What is Ar short for?

Answer 15

Any aryl group

Question 16

How is a formal charge worked out?

Answer 16

Nv - Ne
Nv = valence electrons for neutral atom
Ne = bonding pairs x 1 + lone pairs x 2

Question 17

Name of CH3COCH3

Answer 17

Acetone

Question 18

Name of CH3COOH

Answer 18

Acetic acid

Question 19

Name of CH3CH2OCH2CH3

Answer 19

(diethyl) ether

Question 20

Name of C6H5CH3

Answer 20

Toluene

Question 21

Name of CH3COOCOCH3

Answer 21

Acetic anhydride

Question 22

Name of CHCl3

Answer 22

Chloroform

Question 23

Spacing between atoms is comparable to what?

Answer 23

Wavelength of X-rays

Question 24

What does X-ray crystallography show or not show?

Answer 24

Shows: the position of atoms, uncertainty in the position of atoms and bond lengths
Doesn’t show: double or triple bonds

Question 25

What does X-ray crystallography produce?

Answer 25

Electron density maps

Question 26

Advantages and disadvantages of X-ray crystallography

Answer 26

Advantages: Ultimate method for structural information, gives the location of all atoms
Disadvantages: Need good quality crystals, can be hard to locate H atoms

Question 27

What is the crude way to ionise a sample for mass spectrometry?

Answer 27

Knock electrons out by firing high energy electrons at the vapour
M+ positive molecular ion yielded

Question 28

Outline the electrospray method of ionisation

Answer 28

Sample introduced as charged aerosol droplets
The solvent evaporates in vacuum leaving charged molecules
Detect molecule with ion stuck on
Ion can be +ve or -ve

Question 29

Outline MS/MS technique

Answer 29

Ionize sample
Form molecular ion + fragments
Isolate ion
'parent ion'
Fragment
'daughter ions'

Question 30

Advantages and disadvantages of mass spectrometry

Answer 30

Advantages: gives molecular formula, excellent for analysis of mixtures, a tiny sample is needed
Disadvantages: difficult to interpret, especially for unknowns