Alcohols

Understanding the chemical and physical properties of alcohols is crucial in toxicology

General Properties of Alcohols

Definition: Organic compounds characterized by the presence of one or more hydroxyl (\(-OH\)) groups attached to a carbon atom
Nomenclature: Named by adding the suffix “-ol” to the parent alkane name (e.g., methanol, ethanol)
Classification: Alcohols can be classified as primary, secondary, or tertiary, depending on the number of carbon atoms bonded to the carbon atom bearing the hydroxyl group
Hydrogen Bonding: The presence of the hydroxyl group allows alcohols to form hydrogen bonds with other molecules, including water

Polarity: The hydroxyl group makes alcohols polar molecules
Acidity: Alcohols are weakly acidic due to the ability of the hydroxyl group to donate a proton (\(H^+\))
Reactivity: Alcohols undergo various chemical reactions, including:
- Oxidation: Alcohols can be oxidized to aldehydes, ketones, or carboxylic acids, depending on the alcohol and the oxidizing agent
- Esterification: Alcohols react with carboxylic acids to form esters
- Dehydration: Alcohols can be dehydrated to form alkenes
- Ether Formation: Alcohols react with other alcohols to form ethers
Flammability: Alcohols are flammable

Appearance: Alcohols can be liquids or solids at room temperature, depending on their molecular weight
Boiling Point: Boiling points increase with increasing molecular weight and hydrogen bonding
Solubility: Alcohols with short carbon chains are miscible with water due to hydrogen bonding. Solubility decreases as the carbon chain length increases, because the influence of the nonpolar part of the molecule increases
Viscosity: Alcohols tend to be more viscous than alkanes with similar molecular weights due to hydrogen bonding

Chemical Formula: \(CH_3OH\)
Molecular Weight: 32.04 g/mol
Appearance: Colorless, volatile liquid
Boiling Point: 64.7°C
Solubility: Miscible with water and many organic solvents
Toxicokinetics
- Rapidly absorbed after ingestion or inhalation
- Widely distributed throughout the body
- Metabolized by alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) to formaldehyde and formic acid, which are highly toxic
- Excreted in the urine and as carbon dioxide via the lungs
Toxicity
- Visual disturbances: Blurred vision, decreased visual acuity, blindness
- Metabolic acidosis: Due to the accumulation of formic acid
- Neurological symptoms: Headache, dizziness, confusion, seizures, coma
Analytical Methods: Gas chromatography (GC), enzymatic assays

Chemical Formula: \(C_2H_5OH\)
Molecular Weight: 46.07 g/mol
Appearance: Colorless, volatile liquid
Boiling Point: 78.37°C
Solubility: Miscible with water and many organic solvents
Toxicokinetics
- Rapidly absorbed after ingestion
- Widely distributed throughout the body
- Metabolized by alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) to acetaldehyde and acetic acid
- Excreted in the urine and as carbon dioxide via the lungs
Toxicity
- Central nervous system (CNS) depression: Impaired judgment, slurred speech, ataxia, coma
- Liver damage: Cirrhosis, hepatitis
- Gastrointestinal problems: Gastritis, pancreatitis
- Withdrawal syndrome: Tremors, anxiety, seizures, delirium tremens
Analytical Methods: Gas chromatography (GC), enzymatic assays

Chemical Formula: \((CH_3)_2CHOH\)
Molecular Weight: 60.10 g/mol
Appearance: Colorless liquid
Boiling Point: 82.4°C
Solubility: Miscible with water and many organic solvents
Toxicokinetics
- Rapidly absorbed after ingestion or inhalation
- Widely distributed throughout the body
- Metabolized by alcohol dehydrogenase (ADH) to acetone
- Excreted in the urine and as acetone via the lungs
Toxicity
- CNS depression: Drowsiness, confusion, coma
- Gastrointestinal irritation: Nausea, vomiting, abdominal pain
- Pulmonary edema
Analytical Methods: Gas chromatography (GC)

Chemical Formula: \(C_2H_6O_2\)
Molecular Weight: 62.07 g/mol
Appearance: Colorless, odorless liquid
Boiling Point: 197.3°C
Solubility: Miscible with water and many organic solvents
Toxicokinetics
- Rapidly absorbed after ingestion
- Widely distributed throughout the body
- Metabolized by alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) to glycoaldehyde, glycolic acid, glyoxylic acid, and oxalic acid, which are highly toxic
- Excreted in the urine
Toxicity
- Stage 1 (0.5-12 hours): CNS depression, nausea, vomiting
- Stage 2 (12-24 hours): Cardiopulmonary effects, tachycardia, hypertension, pulmonary edema
- Stage 3 (24-72 hours): Renal failure, flank pain, oliguria
- Calcium oxalate crystals in the urine
Analytical Methods: Gas chromatography (GC), enzymatic assays, osmolal gap calculation

Chemical Formula: \(C_3H_8O_2\)
Molecular Weight: 76.09 g/mol
Appearance: Colorless, odorless liquid
Boiling Point: 188.2°C
Solubility: Miscible with water and many organic solvents
Toxicokinetics
- Rapidly absorbed after ingestion
- Widely distributed throughout the body
- Metabolized to lactic acid and pyruvic acid
- Excreted in the urine
Toxicity
- Generally considered less toxic than ethylene glycol
- High concentrations can cause CNS depression, lactic acidosis, and hyperosmolality
Analytical Methods: Gas chromatography (GC)

Alcohol	Formula	Molecular Weight	Appearance	Boiling Point (°C)	Solubility	Primary Toxic Effects
Methanol	\(CH_3OH\)	32.04	Colorless liquid	64.7	Miscible	Visual disturbances, metabolic acidosis
Ethanol	\(C_2H_5OH\)	46.07	Colorless liquid	78.37	Miscible	CNS depression, liver damage, withdrawal syndrome
Isopropanol	\((CH_3)_2CHOH\)	60.10	Colorless liquid	82.4	Miscible	CNS depression, gastrointestinal irritation
Ethylene Glycol	\(C_2H_6O_2\)	62.07	Colorless liquid	197.3	Miscible	CNS depression, cardiopulmonary effects, renal failure
Propylene Glycol	\(C_3H_8O_2\)	76.09	Colorless liquid	188.2	Miscible	CNS depression, lactic acidosis, hyperosmolality

Selection of Analytical Method: Physical and chemical properties guide the selection of appropriate analytical methods
Sample Preparation: Solubility and stability determine the optimal sample preparation techniques
Interpretation of Results: Understanding metabolism and excretion helps interpret analytical results and assess the severity of poisoning

Accurate Diagnosis: Prompt and accurate identification of the ingested alcohol is crucial for appropriate treatment
Assessment of Severity: Measurement of alcohol concentrations helps assess the severity of poisoning and guide clinical management
Monitoring of Treatment: Serial measurements of alcohol concentrations are used to monitor the effectiveness of treatment and guide further interventions

Alcohol: An organic compound containing one or more hydroxyl (\(-OH\)) groups
Methanol: Methyl alcohol, a highly toxic alcohol
Ethanol: Ethyl alcohol, the alcohol found in alcoholic beverages
Isopropanol: Isopropyl alcohol, a common disinfectant
Ethylene Glycol: A toxic alcohol found in antifreeze
Propylene Glycol: A less toxic alcohol used in various products
Toxicokinetics: The study of the movement of toxic substances within the body
Metabolism: The process by which the body chemically alters a substance
Excretion: The process by which the body eliminates a substance
Alcohol Dehydrogenase (ADH): An enzyme involved in the metabolism of alcohols
Aldehyde Dehydrogenase (ALDH): An enzyme involved in the metabolism of aldehydes
Osmolal Gap: The difference between the measured osmolality and the calculated osmolality of serum or plasma