(13) Aldehydes and Ketones

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What are aldehydes?

Organic compounds containing one or more CHO groups. Considered to be derivatives of the hydrocarbons in which two hydrogen atoms on the same carbon atom have been replaced by an oxygen atom

How are aldehydes named?

-e suffix on the corresponding hydrocarbon is replaced by an -al (ex: methane to methanal)
-Also reflects its relationship to the alcohol from which it’s formed

Where did the term aldehyde come from?

an acronym composed of the first syllabales of the three words alcohol deprived of hydrogen

The reduction of products of carboxylic acids

aldehydes

If not from a hydrocarbon or alcohol, which can an aldehyde be named after?

carboxylic acids

Formic acid, when reduced, results in….

the production of HCHO

How is HCHO produced commercially?

by partially oxidizing methyl alcohol by passing methyl alcohol vapors over sheets of hot copper acting as a catalyst

What are the properties of HCHO?

-Colorless, irritating odor gas
-Highly dehydrating
-has been shown to have detrimental effect on respiratory membranes even as low as 0.05 ppm
-Soluble in water

HCHO is generally avaliable as…

Formalin, an aqueous solution with 37% HCHO by mass or 40% by volume. This also represents the solubility limit of HCHO gas in water.

In order to increase the concentration above the level of formalin, which must you use as an additional solvent?

ethyl alcohol

The number of grams of pure HCHO gas dissolved in 100 mililiters of solution

index

Because embalming fluids are usually diluted befroe injection, how must one calculate them?

calculate the true percentage of HCHO in a solution

HCHO combines with water to form….

Methylene glycol, an unstable substance which is instrumental in the cross linking reaction of embalming preservatives with protein molecules

HCHO polymerizes to form…

paraformaldehyde

What is polymerization?

a reaction between molecules of the same kind that produces a substance having a molecular mass that is approx a multiple of the original substance

The product resulting from polymerization

polymer (means many units)

What are the characteristics of the molecules of paraHCHO?

-form bonds between each other to create very large molecules
-when they become too heavy, they fall out of the solution and precipitate downward (common when bottles of fluid exceed shelf life or experience low temps)

If HCHO is exposed to low pH, what might happen?

The cannizzaro reaction, or polymerization into paraHCHO. This necessitates buffers to bring them to between 6.5 to 9

Why is methyl alcohol frequently to arterial embalming?

safeguard against premature polymerization

While paraHCHO is undesirable in arterial fluid, it works quite well as:

a major preservative in autopsy compounds

When paraHCHO is hydrolyzed by moisture in body tissues, it releases…

HCHO gas

HCHO will decompose if exposed to tissue that is too

alkaline

if HCHO is exposed to tissue that is too alkaline, what will it decompose into?

salt and methanol

HCHO reacts with ammonia to form:

urotropin, a nitrogenous compound that HCHO has a great affinity for, thereby neutralizing the HCHO. this is a common issue when attempting to preserve bodies in advanced states of decomp, cases of uremic poisoning or any other renal disorders.

What are dialdehydes?

Organic compounds that contain two CHO groups

What is the naming convention for dialdehydes?

named according to which dicarboxylic acid they are a reduction of

Glyoxal

simples of the dialdehydes

What is glyoxal?

The reduction product of oxalic acid and an oxidation product of ethylene glycol. Works similarly to HCHO, but imparts a yellowish color to bodies.

What is glutaraldehyde?

Excellent preservatice and germicide. Commonly referred to as a cold chemical sterilant. Operates best at slightly alkaline pH

What must glutaraldehude be activated with to buffer it?

coinjectant

Once buffered, what is the shelf life of glutaraldehyde?

14 days

What makes glutaraldehyde superior to HCHO?

less dehydrating, retains softer texture in skin that is closer to original texture.

What is the disadvantage of glutaraldehyde?

Cost prohibitive

What are ketones?

derivatives of hydrocarbons containing one or more carbonyl group

Both ketones and aldehydes have carbonyl groups, but what sets them apart?

the positioning. Kentones have the group in the middle.

The simplest ketones are produced by:

the oxidation of secondary alcohols

Oxidizing isopropyl alcohol produces…

Dimethyl ketone (acetone)

What dissolves the most organic substances, yet is very soluble in water?

Dimethyl ketone (acetone)

Dimethyl ketone (acetone) is not recomme3nded for use with:

plastic machine parts or hoses

Dimethyl ketone (acetone) is excellent at removing…

road tar, bandage adhesive surfaces from the skin