quiz answers

Here are some answers to the quiz, all the ones I did by hand I will need to give the answers out in class...

1. Assign names to the following hydrocarbons:






2. Draw the structure of: will do on board
i. Cis 5-methyl-3-heptene
ii. 2- Pentanol
iii. 3 Methyl cyclohexene
iv. Trans 2-methyl-2-hexene
v. 2-methyl 1,4-hexadiene

3. i. Arrange the following alcohols in order of INCREASING boiling point

CH3OH CH3CH2CH2OH CH3CH2CH2CH2OH HOCH2CH2CH2CH2OH
ii. Explain your reasoning
All alcohols exhibit hydrogen bonding. Those with more than 1 OH group will experience greater hydrogen bonding.
Bigger molecules are more easily polarized and hence experience greater London dispersion forces

4. Explain why we ‘recrystallized’ our synthesised Xylene Sulfonic Acid crystals
5.
To increase the purity. Crystals a re dissolved in hot solution. The solution is then allowed to cool. As the solution cools the solubility of compounds in solution drops. This results in the desired compound dropping (recrystallizing) from solution. The slower the rate of cooling, the bigger the crystals formed.

6. Which of the following alcohols could be oxidized to an aldehyde
The primary alcohol – the one with 2 C-H bonds on the C bonded to OH

7. He following ester could be made from which carboxylic acid and alcohol (draw the structures and name)



8. Balance the following equation:

3 CH3CH2OH + 2 Cr2O72- + 16 H+ → 3 CH3COOH + 4 Cr 3+ + 11 H2O

In this reaction the dichromate is oxidizing ___ethanol_______ to _______ethanoic acid__________

9. Complete the following equations with reactants or products and/or conditions






10. Draw 3 structural isomers of C3H8O try naming the 3 that you draw.
Will do on board

11. In the Organic compound CH3X, the weight % of X is 32, what is X? Lithium

12. The Lewis structure of the following organic molecule, what are the approximate bond angles at the points mark a,b and c






13. What is the hybridization of the C atoms labelled a and b in the molecule

14. Explain briefly why Phenol is more acidic than ethanol

The phenoxide ion C6H5-O- is stable as the non bonding electrons are delocalized into the ring.

15. Complete the following reaction
2Na(s) + 2C2H5OH(l) → 2C2H5ONa + H2 sodium ethoxide is a strong base (conjugate base of the ethanol(weak acid)
16. Explain why benzene does not readily undergo addition reactions
It would destabilise the planar hexagon ring structure, which is stable due to delocalisation of electron density over the molecule

17. Why will hexane not dissolve in water?
It is non-polar, water is polar

18. Carboxylic acids are weak acids, however they will readily lose a proton to form the carboxylate anion (the conjugate base). Explain why the carboxylate anion formed is a stable ion?
It can exist as 2 resonance forms. The charge can be spread over a wide area

19. Why should a reflux condenser never be plugged at the top?
The pressure build up will cause the apparatus to explode

20. Base catalysed hydrolysis of an ester is also known as ___________?
Saponification

21. Why would the Cis isomer of 2-butene have a slightly higher boiling point than trans 2-butene?
The slight dipole moments of the C-H bonds cancel out in the trans isomer but not in the cis form leading to a slight increase in Intermolecular forces.
However trans isomers pack together more efficiently in the solid form and hence tend to have slightly higher melting points