1. OCHM – Organic Synthesis
Question Information
Q-Bank
MCAT
Sim
Non-Sim
Subject
Organic Chemistry
Foundation
OCHM – Organic Synthesis
Validity
5 years
Author(s)
Reyes, V. M.
Reviewer(s)
Editor(s)
Passage Information
Passage ID
Media ID(s)
Passage Stem
In the early 1830’s, when organic chemistry was still in its infancy, the early organic chemists usually performed only separation, purification and identification of pre-existing organic compounds or mixtures thereof, such as plant and animals extracts commonly referred to as “natural products.” The conceptual norm then was called “Vitalism,” which postulated that organic substances can only be produced by living organisms by the actions of some “vital force”, while inorganic compounds were synthesized from non-living matter, which was presumed to lack such vital force.
More than 100 years later, organic chemistry became firmly established as a major branch of chemistry. In this modern day and age, perhaps the largest and most active area of organic chemistry is synthetic organic chemistry. Today the reason why many

2. a young chemists will choose to specialize in organic chemistry is to do ‘synthetic organic chemistry,’ that is, to be able to synthesize new organic compounds which have novel properties as drugs, materials for specialized applications (e.g., biomaterials), etc.
In this passage we shall focus on the Grignard reaction, an important way to form new C-C bonds, and a prime example of a synthetic organic reaction. Before a Grignard reaction is carried out, the synthetic chemist must prepare what is called a Grignard reagent. A Grignard reagent is an organometallic compound of the form “R-Mg-X” where R is an alkyl or aromatic group (or aryl group, “Ar-Mg-X”), and X is a halide (except flouride). It is prepared by adding the alkyl (or aryl) halide to small trimmings of magnesium metal suspended in dry liquid ether (e.g., ethyl ether or THF) and heating the mixture:
R-X R-Mg-X
Mg in dry ether
+heat
The Grignard reagent can then be reacted with an aldehyde or a ketone in a weakly acidic solution to form a secondary or tertiary alcohol adduct, respectively (plus a precipitate of Mg(OH)X, to be removed in a subsequent step): O OH = H+ -
R1-Mg-X R2-C-R3
R2-C-R3
+ Mg(OH)X ↓ - R1
R1, R2 and R3 are three alkyl groups which may or may not be identical to each other. For aldehydes, R2 or R3 is a hydrogen, and the resulting alcohol is a secondary one, while for ketones, it will be a tertiary alcohol, as shown above.
For example, heating bromobenzene in THF with metallic Mg yields:
Mg-Br Mg ∆
Then, adding acetone in a slightly acidic solution yields: OH H+
Mg-Br +
Mg(OH)Br ↓ +
acetone

3. Question Attributes #1 (QID: 000000)
Passage References
PMID/Page #
Title of Publication or Book
Type
R. Brewster & W. McEwen, Organic Chemistry textbook
R. W. Griffin, Jr., Modern Organic Chemistry textbook
(N/A)
en.wikipedia.com, youtube.com internet
(N/A)
Author’s own lecture notes
Question Attributes #1 (QID: )
Topic Blueprint
The Grignard Reaction
Competency
MCAT: BS-2: Application of Concepts & Principles
To gain an understand of the Grignard reaction and be able
to predict the product of the reaction given the reactants.
Objective
Media ID(s)
Question ID
Question Stem #1
Predict the molecular structure of the product of the following two-step reaction:
ethyl iodide
ethyl (Mg) iodide

4. isobutyraldehyde ethyl (Mg) iodide II Answer Choices #1 A) I B) C) IIIIV
Correct: A)
(Cont’d. on the next page.)

5. correspond to the carbonyl carbon of the reactant aldehyde.
Explanation #1
The correct choice is B. Remember that the R or Ar (organic) group of the Grignard
reagent attaches to the carbonyl carbon of the aldehyde, and the aldehyde’s carbonyl
oxygen becomes oxidized to an OH group. This becomes more apparent if the C-C bond indicated in the above figure, which is actually molecule II, is rotated 180ᵒ.
(Choice A) This choice is incorrect because the attachment of the OH group does not
correspond to the carbonyl carbon of the reactant aldehyde.
(Choice C) This choice is incorrect; this molecule has both an ether and an alcohol
functional group, and the Grignard reaction does not produce an ether.
(Choice D) This choice is incorrect for the same reason as choice A: the location of
the OH group is incorrect.

6. to predict the product of the reaction given the reactants.
Educational objective: To gain an understand of the Grignard reaction and be able
to predict the product of the reaction given the reactants.
References #1
PMID/Page #
Title of Publication or Book
Verifications #1
Yes / No
The question is at the Application or higher cognitive level.
Yes / No
The question is based on a realistic clinical scenario.
Yes / No
The question has at least one close distracter, and other options have
educational value.
Yes / No
The question is appropriate to the entry level of nursing practice.
Yes / No
The explanation is short and concise, yet thorough.
Yes / No
The question has an appropriate table/flow chart/illustration.