Special Sub-Topic: Ethers and Epoxides
|Are ethers and esters the same thing?|
N. The general formula for ethers is R-O-R', where R and R' are alkyl or aryl groups. On the other hand, the general formula for esters is R-O-O-R'. Esters can be synthesized via esterification processes between alcohols and carboxylic acids.
|What is the name given to the ether with the chemical formula CH3CH2-O-CH2CH3?|
All of these (Ethoxyethane, Ethyl ether, Diethyl ether). All of these are acceptable names for CH3CH2-O-CH2CH3. It is a symmetrical ether. Ethoxyethane is the IUPAC (International Union of Pure and Applied Chemistry) name while ethyl ether and diethyl ether are the common names.
|Can ether molecules form hydrogen bonding among themselves?|
N. The formation of hydrogen bonding requires hydrogen atoms from the -OH group as electron donors and non-bonding lone pairs of electrons as electron acceptor. There are non-bonding lone pairs of electrons in ethers, namely from the oxygen atoms, but there are no -OH groups in ethers. Unlike alcohols, ethers do not form hydrogen bonds among the molecules themselves. This accounts for the fact that the boiling point of alcohol is higher than that of ether.
|Which of the following properties makes ether a more preferable solvent than alcohol?|
Lower boiling point. Ether's low boiling point simplifies evaporation. Alcohols have higher boiling points because of the hydrogen bonding.
|Can ethers dissolve both polar and non-polar compounds?|
Y. Generally, polar solvents dissolve polar compounds while non-polar solvents dissolve non-polar compounds. Ethers are special because they dissolve both polar and non-polar compounds.
|The Williamson ether synthesis is one of several ways to synthesize ethers. What type of mechanism is involved in this synthesis?|
SN2 (Nucleophilic bimolecular substitution). The Williamson ether synthesis is the most reliable and versatile methods to synthesize ethers, compared to the less-preferred alkoxymercuration-demercuration and bimolecular dehydration methods. It involves SN2 (nucleophilic bimolecular substitution) mechanism, where the ionized alkoxide ion will attack the unhindered primary alkyl halide.
|An epoxide is a cyclic ether with 3 atoms on its ring (2 carbons and 1 oxygen). What is the alternative name for epoxides?|
Oxiranes. Epoxides are named based on their parent compound, oxiranes. For example, the chemical name for CH2-O-CH2-CH3 (the O is linked to the first and the second carbon) is methyloxirane.
|We can react alkene with acid to produce epoxides. Which of the following acids is suitable for this purpose?|
Meta-chloroperoxybenzoic acid (MCPBA). We should use only weak acid such as meta-chloroperoxybenzoic acid (MCPBA). MCPBA will oxidize the alkene's double bond to form epoxides. If we use strong acid, the epoxide's ring will open up and we will get glycols and not epoxides.
|Epoxides can react under both acidic and basic conditions.|
T. For the acid-catalyzed (in the presence of H+) ring opening reaction, after the protonation of the epoxide, a strong electrophile will be formed. Then, the alcohol (CH3CH2OH) (the nucleophile) will add to the more substituted carbocation.
On the other hand, for the base-catalyzed (in the presence of CH3CH2O-) ring opening reaction, the CH3CH2O- ion will attack the less hindered carbocation through SN2 mechanism.
|Between a straight-chain ether and a cyclic ether (such as epoxide), which one is more reactive?|
Cyclic & cyclic ether & epoxide. Straight chain ethers are very unreactive. So, they can be used as solvents for many chemical reactions. However, cyclic ethers such as epoxides are very reactive because of the ring strains. They tend to react with other compounds to "open up" the ring to achieve higher stability.
Did you find these entries particularly interesting, or do you have comments / corrections to make? Let the author know!
Send the author a thank you or
Submit a correction