Tải bản đầy đủ - 0trang
4 Compounds Containing Multiple Functional Groups
Lysergic acid diethylamide (LSD) is named as an amide derivative, a functional group we did not discuss in our study of
Take a moment and compare your right hand to your left. They are virtually identical in most respects, but a right glove will
not fit on your left hand. Your hands are mirror images that are not superimposable on one another, a fact you may have never
considered, nor had cause to, until now. This property of “handedness,” or chirality (chiral: Greek-“handed”), is characteristic of organic compounds containing chiral carbons – any carbon bound to four different groups. The nonsuperimposable
mirror images of chiral molecules are stereoisomers called enantiomers. Stereoisomers have the same chemical formula but
differ in the spatial arrangement of atoms. Enantiomers have almost identical physical and chemical properties; for example,
same melting points, boiling points, and solubility. Your hands, which themselves are enantiomers, are clearly different from
one another; by analogy, there must be a difference that distinguishes the enantiomers of chiral molecules. The search for this
difference leads us to an unlikely candidate, the electromagnetic spectrum, or light. Enantiomers exhibit optical activity by
rotating plane-polarized light in equal, but opposite directions. One enantiomer will rotate light clockwise (right) and is said
to be dextrorotary (or also dextrorotatory), whereas the other will rotate light counterclockwise (left) and is referred to as
levorotary (or also levorotatory). The direction of rotation is indicated in the names of optically active molecules using a
“(d)” or “(+)” for dextrorotary, for example, (d)-morphine or (+)-morphine, and “(l)” or “(–)” for levorotary, for example,
(l)-morphine or (–)-morphine. The optical activity of a specific molecule is determined using a polarimeter to measure the
rotation of polarized light. The R/S convention is a quick, reliable method used to distinguish enantiomers without the necessity of polarimetry experiments. The details of this method are beyond the scope of this text; however, a basic overview is
presented because this convention has relevance in our study of forensic chemistry.
The four different groups attached to chiral carbons are assigned priorities using the Cahn–Ingold–Prelog system (not
discussed). The structure is oriented in a manner that allows the viewer to look down the carbon bond containing the lowest priority group, usually a carbon–hydrogen bond. The remaining groups are arranged in a circular configuration facing
the viewer. One simply counts the remaining groups 1, 2, 3; if counting is in a clockwise direction, the R-isomer is present
(rectus: Latin-“right”). If counting is counterclockwise, the S-isomer is present (sinister: Latin-“left”). It is worth noting
that the R/S designation does not indicate optical rotation; it is simply a quick, easy method used to differentiate enantiomers. For example, (S)-glyceraldehyde is levorotary whereas (S)-alanine is dextrorotary. An understanding that optically
active isomers exist, and the basic recognition of conventions used to differentiate them, is far more valuable than knowing the exact direction of rotation, which is usually of little consequence.
A sound foundation in organic chemistry is an absolute necessity in forensic investigation. Forensic scientists must be
skilled in the interpretation of complex chemical procedures and results. In addition, they must be able to communicate this
knowledge to members of a jury using common terminology. This ability is specific to forensics and generally not found in
other areas of science. It is developed through knowledge, training, and experience and distinguishes forensic scientists as
some of the most versatile and diverse in the scientific community.
Define organic chemistry.
Please define the term functional group to members of the jury.
Name the first ten alkanes with their chemical formulas.
Draw the structural formula and condensed structural formula for heptane.
Draw methane using the wedge convention.
Draw the following:
Name the first four alkenes.
Draw the structures with a chemical formula C4H8 (there are three), and name each.
Draw the following:
Explain why acetylene is not a member of the alkene class.
Define aromatic character.
Name the following:
13. Draw the following alcohols and classify each as primary, secondary, or tertiary.
14. Discuss alcohol solubility in water.
15. Why is acetone the smallest member of the ketone class?
16. Draw 3-hexanone and butanone.
17. Name the following:
18. Draw the following:
(a) 2-chlorobutanoic acid
(b) Hexanoic acid
(c) Acetic acid
19. Classify the following amines as primary, secondary, or tertiary.
20. Identify all functional groups in the following:
Jones, M. Organic Chemistry, 3rd ed.;W.W. Norton & Company: New York, 2004, (Chapter 21).
Tools of Forensic Chemistry
Drugs, narcotics, and controlled substances may be defined as:
• Any substance that causes dependency in humans.
• Any substance intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease(s).
• Any substance that alters the mind, senses, mood, or thoughts.
• Any substance listed in the Official United States Pharmacopeia, the Official Homeopathic Pharmacopeia of the United
States, or the Official National Formulary.
Origin of Drugs (Narcotics)
Heroin, cocaine, tetrahydrocannabinol (THC), bufotenine, psilocin, and psilocybin are narcotics derived from either plants
or animals. Heroin is extracted from the poppy plant using a relatively simple procedure, and cocaine is easily isolated from
coca plants. THC can be extracted from marijuana plants or its effects can be obtained from direct use of the dried plant (i.e.,
smoking). LSD is extracted from the ergot of rye and psilocin/psilocybin is isolated from mushrooms. Bufotenine is collected
from the skin glands of the Bufo toad or from toadstool mushrooms.
Synthetic drugs are derived from mineral sources using a wide range of chemical processes. Barbiturates (produced from
pyrimidine), phenethylamine analogs (except drugs in Khat or peyote plants), and the tryptamine family of drugs represent
common examples of synthetic drugs.
Psychotropic Drugs (Mind Altering)
“Excitantia”: Stimulants, such as caffeine and amphetamine
“Inebriantia”: Intoxicants, such as ethanol and nitrous oxide
“Hypnotica”: Hypnotics, such as methaqualone and mecloqualone
“Euphorica”: Analgesics/tranquilizers, such as morphine and heroin
“Phantastica”: Hallucinogens, such as psilocyn and mescaline
Psycoanaleptique: Cocaine and amphetamine
J.I. Khan et al., Basic Principles of Forensic Chemistry, DOI 10.1007/978-1-59745-437-7_5,
© Springer Science+Business Media, LLC 2012
Psycholeptiques: Morphine and heroin
“Entactogens”: MDMA (3,4-methylenedioxymethamphetamine, ecstacy) and MDA (3,4-methylenedioxyamphetamine)
Psychodysleptiques: Mescaline and LSD (lysergic acid diethylamide)
Dependence and Addiction
Physical dependency is a condition resulting from chronic drug use that is characterized by the physiological side effects of
tolerance and withdrawal.
Tolerance is the need to ingest progressively larger amounts of a drug to maintain a desired effect. It is a condition characterized by a marked decrease in both time duration and intensity of analgesia, euphoria, and sedation associated with a specific
dosage. Tolerance development is inconsistent and unpredictable; toxic side effects often accompany increased tolerance.
Withdrawal is a term used to describe the unfavorable physical symptoms that result if drug use is suddenly stopped or
dosage is drastically reduced. Withdrawal symptoms can range from mildly unpleasant to life threatening and their severity
depends on a number of factors, i.e.: age, sex, type of drug, frequency and duration of abuse, daily dosage, route of administration, and concurrent abuse of other drugs. In general, short-term narcotics tend to produce shorter, more intense withdrawal symptoms, while longer-acting narcotics produce withdrawal symptoms that are protracted but less severe. The
symptoms associated with heroin/morphine addiction are usually experienced just prior to the next scheduled dose. Initial
symptoms may include watery eyes, runny nose, yawning, and sweating, followed by restlessness, irritability, loss of appetite, nausea, and tremors. The advanced stages are marked by severe depression, vomiting, elevated heart rate and blood
pressure, muscle spasms, chills, excessive sweating, and pain in the bones, back muscles, and extremities. A suitable narcotic
can be administered at any stage of withdrawal that will dramatically reduce the symptoms. Without intervention, the effects
of withdrawal will slowly subside and most of the physical symptoms will disappear in 7–10 days.
Drug users often abuse a specific or preferred drug, and it is not uncommon to substitute drugs that produce similar effects
(often the same drug class). Drugs within a class are often compared using terms, such as potency and efficacy. Potency
defines the amount (dosage) of a drug that must be taken in order to produce a desired effect. Efficacy is the capacity of a
drug to produce a given (desired) effect, regardless of dose.
The physical effects produced by any drug can vary significantly and are largely dependent on the dose, route of administration,
and individual sensitivity to the drug. Concurrent use of several types of drugs may either enhance or block specific effects. As a
result, abusers often take more than one drug in an effort to increase the desired effects, while minimizing unwanted side effects.
This practice can dramatically increase the risks associated with drug abuse because the overall effects cannot be accurately predicted. This suggests that a genetic component may exist that predisposes individuals to either drug toxicity or addictive behavior.
Psychological dependency is a perceived “need” or “desire” for a drug and is commonly associated with addiction.
Individuals who are psychologically dependent often feel (or believe) that they cannot function normally without continuous drug use. Psychological dependency can last much longer than physical dependency and is a primary reason for
relapse after a period of either treatment or abstinence.
The psychological dependence associated with narcotic addiction is complex and protracted. Addicts often ponder
drug use long after the physical need for the drug has subsided. They may feel either uneasy or overwhelmed while
performing daily activities without the influence of drugs (sober). There is a high probability of relapse after narcotic
withdrawal, if changes are not made to either the addict’s physical environment or behavioral motivators (associates).
There are two major patterns of narcotic abuse or dependence observed in the United States. One involves individuals whose drug use was initiated within the context of medical treatment. These individuals escalate use by obtaining
fraudulent prescriptions or elicit drugs. The other, more common pattern is initiated outside the clinical setting through
either the experimental or recreational use of narcotics. The majority of individuals in this category may abuse narcotics periodically for either months or even years. Although they may not become addicts, the social, medical, and legal
consequences of their behavior are very serious. Some experimental users will escalate narcotic use to the point of
physical and psychological dependency. Individuals initiating drug use at an early age are more likely to progress from
casual use to dependence and addiction.