Examples of ethers in everyday life

Examples of naturally occurring molecules which contain a aldehyde or ketone functional group are shown in the following two figures. The compounds in the figure 9. Many of these molecular structures are chiral and have distinct stereochemistry. When chiral compounds are found in nature they are usually enantiomerically pure, although different sources may yield different enantiomers.

For example, carvone is found as its levorotatory R -enantiomer in spearmint oil, whereas, caraway seeds contain the dextrorotatory S -enantiomer. In this case the change of the stereochemistry causes a drastic change in the perceived scent. Aldehydes and ketones are known for their sweet and sometimes pungent odors. The odor from vanilla extract comes from the molecule vanillin. Likewise, benzaldehyde provides a strong scent of almonds.

Because of their pleasant fragrances aldehyde and ketone containing molecules are often found in perfumes. However, not all of the fragrances are pleasing. In particular, 2-Heptanone provides part of the sharp scent from blue cheese and R -Muscone is part of the musky smell from the Himalayan musk deer. Lastly, ketones show up in many important hormones such as progesterone a female sex hormone and testosterone a male sex hormone. Notice how subtle differences in structure can cause drastic changes in biological activity.

The ketone functionality also shows up in the anti-inflammatory steroid, Cortisone. Acetone is also produced as a breakdown product of acetoacetic acid. Acetone can then be excreted from the body through the urine or as a volatile product through the lungs. Normally, ketones are not released into the bloodstream in appreciable amounts.

Instead, ketones that are produced during lipid metabolism inside cells are usually fully oxidized and broken down to carbon dioxide and water. This is because glucose is the primary energy source for the body, especially for the brain. Glucose is released in controlled amounts into the bloodstream by the liver, where it travels throughout the body to provide energy.

For the brain, this is the primary energy source, as the blood-brain barrier blocks the transport of large lipid molecules. However, during times of starvation, when glucose is unavailable, or in certain disease states where glucose metabolism is disregulated, like uncontrolled diabetes mellitus, the ketone concentrations within blood rises to higher levels to provide an alternative energy source for the brain. Ketoacidosis can be a life threatening event.

Ketones can be easily detected, as acetone is excreted in the urine. In severe cases, the odor of acetone can also be noted on the breath. So the carbonyl carbon is also attached directly to an alcohol. In the ester functional group, the carbonyl carbon is also directly attached as part of an ether functional group. The name carboxyl comes from the fact that a carbonyl and a hydroxyl group are attached to the same carbon.

Carboxylic acids are named such because they can donate a hydrogen to produce a carboxylate ion. The factors which affect the acidity of carboxylic acids will be discussed later. Esters An ester is an organic compound that is a derivative of a carboxylic acid in which the hydrogen atom of the hydroxyl group has been replaced with an alkyl group.

The general formula for an ester is shown below. The R group can either be a hydrogen or a carbon chain. The steps for naming esters along with two examples are shown below. Boiling Points, Melting Points and Solubility Carboxylic acids can form hydrogen bond dimers which increases their boiling points above that of alcohols of similar size Table 9. Esters, like aldehydes and ketones, are polar molecules. Thus, their boiling points are higher than ethers and lower than aldehydes and ketones of similar size.

Low molecular weight carboxylic acids tend to be liquids at room temperature, whereas larger molecules form waxy solids. Carboxylic acids that range in carbon chain length from 12 carbons are typically called fatty acids, as they are commonly found in fats and oils. Comparable to other oxygen containing molecules, the short-chain carboxylic acids tend to be soluble in water, due to their ability to form hydrogen bonds.

As the carbon chain length increases, the solubility of the carboxylic acid in water goes down. Esters can also hydrogen bond with water, although not as efficiently as carboxylic acids, and thus they are slightly less soluble in water than carboxylic acids of similar size. Carboxylic acids typically have in unpleasant, pungent and even rancid odors.

The smell of vinegar, for example, is due to ethanoic acid also known as acetic acid. The odor of gyms and unwashed socks is largely caused by butanoic acid, and hexanoic acid is responsible for the strong odor of limburger cheese. Due to their acidic nature, carboxylic acids also have a sour taste as noted for vinegar and the citric acid found in many fruits. Esters, on the otherhand, have enjoyable aromas and are responsible for the aroma of many fruits and flowers.

Esters can also have fruity flavors. Commonly Used Carboxylic Acids and Esters Carboxylic acids and esters are common in nature and are used for a multitude of purposes. For example, ants in the Formicidae family use the simplest carboxylic acid, formic acid, as both a chemical defense and as an attack to subdue prey Figure 9. Acetic acid also gives sourdough bread its sharp taste and accounts for the sour flavors in wine.

Citric acid is found in many fruits and accounts for their sour flavor. Other carboxylic acids such as PABA and glycolic acid are used in the cosmetic industry. PABA which is produced by plants, fungi, and bacteria is a common component of food and is related in structure to the vitamin folate.

In PABA was patented as one of the first compounds used in the manufacture of sunscreen. However, its use has fallen out of favor since the mids due to concerns that it may increase cellular UV damage, as well as contribute to allergies. In food processing it is used as a preservative and in the skin care industry it is used most often as a chemical peel to reduce facial scarring by acne.

A Formic acid is the defense toxin used by ants in the Formicidae family. The photo on the left shows various flavors of vinegar at a market in France. Photo by Georges Seguin C Citric acid is a common component of fruit, providing a sour taste. It was patented in for its use in sunscreen products. However, due to safety concerns and allergic response, the use of PABA has been discontinued for this purpose.

Suncreen photo provided by HYanWong E Glycolic acid is commonly used in cosmetics as a chemical peel used to reduce scarring by acne. Glycolic study provided by Jaishree Sharad. Esters are readily synthesized and naturally abundant contributing to the flavors and aromas in many fruits and flowers.

For example, the ester, methyl salicylate is also known as the oil of wintergreen Figure 9. The fruity aroma of pineapples, pears and strawberries are caused by esters, as well as the sweet aroma of rum. Photo of A Gaultheria procumbens, the producer of the oil of wintergreen is provided by: LGPL B pineapple photo provided by: David Monniaux, and C Photo of rum provided by: Summerbl4ck Esters also make up the bulk of animal fats and vegetable oils as triglycerides.

The formation of lipids and fats will be described in more detail in Chapter In this section, we will discuss two major types of reactions. The first are the dehydration reactions and the second are the oxidation reactions. Alcohols can also be involved in addition and substitution reactions with other functional groups like aldehydes, ketones, and carboxylic acids.

These types of reactions will be discussed in more detail within the aldehyde and ketone, and carboxylic acid sections. Dehydration Elimination Reactions In chapter 8, we learned that alcohols can be formed from the hydration of alkenes during addition reactions. We also learned that the opposite reaction can also occur.

Their use in water-based coatings is an example how this property can be used. These substances act as solvents and as coalescing aids and coupling solvents in paint formulations. Their coalescing aid property is essential for high quality film formation in water-based paints, while the solvents power of the materials is needed e. The higher molecular weight E-series glycol ethers triethylene glycol ethers or higher homologues are also used in hydraulic brake fluids.

E-series glycol ethers are also used as intermediates and undergo further chemical reactions e. P-series Propylene Glycol Ethers are high-performance industrial solvents. P-series glycol ethers are based on reacting propylene oxide with varying chain alcohols. They are used for paints and coatings, cleaners, inks, and a variety of other applications.

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