1) The Alkyne module in ORGO will be a big help to you: https:// classes.yale.edu/chem220a/ studyaids/index/index.html.   2 Diethyl ether can be prepared by an SN2 reaction between sodium C2H5ONa and ethyl bromide in ethanol (Williamson ether synthesis). When (E)-4-octene (A) reacts with Cl2/H2O, compound B (C8H17ClO) is formed. When B reacts with potassium tert-butoxide, B is converted into C (C8H16O) and tert-butyl alcohol D. What are the structures of B and C. Explain the steps and pay attention to stereochemistry. [10/20 lecture]

Alexander Williamson 1824-1904

3) When (R)-6-methyl-3-octyne (1) is heated with NaNH2, a base-catalyzed rearrangement occurs

(p. 395) producing the sodium salt of a terminal acetylene, optically active (R)-1-sodio-6- methyl-1-octyne (2). Addition of water to 2 provides (R)-6-methyl-1-octyne (3). Your text (p.395) states

that an internal acetylene, which is more stable* than a terminal acetylene, is usually formed when KOH at

200 oC is used in such a rearrangement. Yet when NaNH2 is employed, the terminal alkyne and not the

internal alkyne is formed. This reaction is driven by the irreversible formation of 2. Compare

[https://classes.yale.edu/chem220a/ studyaids/pKa.html] the pKa's of water, a terminal acetylene and NH3

to explain these results. The acetylene group, i. e., the triple bond, does not migrate to the other end of the

carbon chain to produce ultimately 3-methyl-1-octyne (4). Why? [Hint: Think about what would happen

at the stereogenic carbon if the rearrangement occurred in this direction to produce terminal alkyne 4.] [* --

> Compare the heats of formation of 1-butyne and 2-butyne. Note that they are both less stable than their

respective elements. https://classes.yale.edu/chem220a/studyaids/thermo/heats-formation.html]

4) In problem 3, two optically active, diastereomeric allenes, 6-methyl-2,3-octadiene, serve as intermediates

in the conversion of alkyne 1 (in problem 3) to a second alkyne A, (R)-6-methyl-2-octyne, before 2

(problem 3) is formed. Explain and illustrate. [See, https://classes.yale.edu/chem220a/studyaids/isomers

/isom_intro/isomer.html and/or p. 199 for additional help.]

5) An unknown compound A (C6H10) reacts with Li/NH3 to form B (C6H12). Ozonolysis and dimethyl

sulfide reduction of compound B affords only n-propionaldehyde C. Treatment of B with Br2 in CCl4 gives D

while OsO4 oxidation of B gives E. What are the structures of A-E? Show your reasoning; pay attention

to stereochemistry.

6) Design a synthesis of meso-3,4-hexanediol. Acetylene and ethylene are the only sources of carbon

available to you. All reagents are available.

7) An optically active compound A (C6H13Br) reacts with C2H5ONa in C2H5OH to form a single

compound (E)-B, C6H12. Ozonolysis of B forms an aldehyde (not formaldehyde) C and the only C4

ketone D. What are the structures of A-D? [You will not be able to determine which enantiomer of A it

is.]

8) Our mutual friend*, Dr. Knowitall, decides to prepare only 2-octanone from 2-octyne by hydration in the

presence of stoichiometric HgSO4. What two pieces of advise do you have to offer him/her? [Hint: If

you're stumped and haven't read the Alkyne module in ORGO, now would be a good time.]

* Not to be confused with Charles Dickens's, "Our Mutual Friend". Dickens did make the following

observations about our fair city in his "American Notes" during his visit in 1842.

New Haven, known also as the City of Elms, is a fine town. Many of its streets (as its alias sufficiently

imports) are planted with rows of grand old elm-trees; and the same natural ornaments surround Yale

College, an establishment of considerable eminence and reputation. The various departments of this

Institution are erected in a kind of park or common in the middle of the town, where they are dimly visible

among the shadowing trees. The effect is very like that of an old cathedral yard in England; and, when

their branches are in full leaf, must be extremely picturesque. Even in the winter-time, these groups of

well-grown trees, clustering among the busy streets and houses of a thriving city, have a very quaint

appearance: seeming to bring about a kind of compromise between town and country; as if each had met

the other half-way, and shaken hands upon it; which is at once novel and pleasant.

[http://wsrv.clas.virginia.edu/~jlg4p/dickens/amnotes/dkstc.html]