University:
Purdue University
Course:
CHM 11100 | General Chemistry
Academic year:

2024
Views:

396

Pages:

2
Author:

apallirasbnc4

Question 4 I am a Third year college student. So, following are the topics as part of my report in the subject of Organic Chemistry, can you help me understand in simple terms so that I can deliver my report smoothly and accordingly in front of my instructor and classmates. Polarization of the carbonyl group creates dipole-dipole attractions between the molecules of ketones and aldehydes, resulting in higher boiling points than for hydrocarbons and ethers of similar molecular weights. Ketones and aldehydes have no O-H or NH bonds, however, so their molecules cannot form hydrogen bonds with each other. Their boiling points are therefore lower than those of alcohols of similar molec- ular weight. The following compounds of molecular weight 58 or 60 are ranked in order of increasing boiling points. The ketone and the aldehyde are more polar and higher-boiling than the ether and the alkane, but lower-boiling than the hydrogen- bonded alcohol. CH₂CH₂CH₂CH₂ butane bp 0°C CH-O-CH2CH3 methoxyethane bp 8 °C 0 CH₂CH₂-C-H propanal bp 49 °C CH3-C-CH3 acetone bp 56 °C CH₂CH₂CH₂-он propan-1-ol bp 97 °C The melting points, boiling points, and water solubilities of some representative ketones and aldehydes are given in Table 18-3. Although pure ketones and aldehydes cannot engage in hydrogen bonding with each other, they have lone pairs of electrons and can act as hydrogen bond acceptors with other compounds having O-H or N-H bonds. For example, the OH hydrogen of water or an alcohol can form a hydrogen bond with the unshared electrons on a carbonyl oxygen atom. Because of this hydrogen bonding, ketones and aldehydes are good solvents for polar hydroxylic substances such as alcohols. They are also relatively soluble in water. Table 18-3 shows that acetaldehyde and acetone are miscible (soluble in all propor- tions) with water. Other ketones and aldehydes with up to four carbon atoms are fairly soluble in water. These solubility properties are similar to those of ethers and alcohols, which also engage in hydrogen bonding with water. Formaldehyde and acetaldehyde are the most common aldehydes. Formaldehyde is a gas at room temperature, so it is often stored and used as a 40% aqueous solution called formalin. When dry formaldehyde is needed, it can be generated by heating one of its solid derivatives, usually trioxane or paraformaldehyde. Trioxane is a cyclic trimer, containing three formaldehyde units. Paraformaldehyde is a linear polymer,containing many formaldehyde units. These solid derivatives form spontaneously when a small amount of acid catalyst is added to pure formaldehyde.Acetaldehyde boils near room temperature, and it can be handled as a liquid. Acetaldehyde is also used as a trimer (paraldehyde) and a tetramer (metaldehyde), formed from acetaldehyde under acid catalysis. Heating either of these compounds provides dry acetaldehyde. Paraldehyde is used in medicines as a sedative, and metaldehyde is used as a bait and poison for snails and slugs. Answer 039;s section on aldehydes and ketones In conclusion, we have discussed the concepts of polarization, hydrogen bonding, and boiling points in regard to ketones and aldehydes. We have also explored the solubility and uses of these compounds. I hope this helps you deliver a smooth and accurate report in your Organic Chemistry class. Best of luck with your presentation!