Alexandria University Faculty of Engineering Chemical Engineering department

Nov, 2013 2013 Course title Number: organic chemsitry 1 ( ( Time allowed:1 hr 1:.

Answer the following Questions

State whether the following statements are false or true and correct the false ones:-I Electropositivity is a measure of the ability of an element to attract electrons. -1

1 reaction depends on the concentration of the nucleophile.Nrate of an SThe -2 2I 2Br 2Cl 2The order of reactivity of the halogens with alkanes is F -3

Lithium fluoride consists of a regular stack of Li and F ions held together by strong -4dipole-dipole interaction forces.

There is a small energy barrier to rotation associated with group joined by a double -5bond

Both the magnitude and the direction of the individual bond dipole moments in a -6molecule can affect the overall dipole moment of the molecule.

in determining size of the atom is more important than its electronegativityThe -7how well it bears its negative charge 8- The structure of the alkyl halide may affect the mechanism of nucleophilic substitution which predominates. 9- In SN2 reaction, doubling the hydroxide ion concentration would double the rate of the reaction

The carbanion is a strong electrophile; it reacts very fast with either strong or -10weak nucleophile. 11- Primary alkyl halides and methyl halides can undergo SN1 reactions. 12-In general symmetrical molecules have no dipole moment. 13- The second step of SN1 reaction mechanism is the rate-determining step. 14- Sec-butyl bromide and tert-butyl bromide are two constitutional isomers to each other. 15- The higher the percent of s-character of the hybrid orbital, the closer the lone pair is held to the nucleus, and the more strong the conjugate base II- Write The reaction mechanism of tert-butyl bromide with water to form 2-methylpropene. How can the yield of 2-methylpropene be increased?

III-Choose the correct answer from A, B,C or D:

1-This species is a carbon-based Lewis acid: A) CH4 B) HCCl3 C) CH3+ D) :CH3- 2. Select the reagents necessary to convert 3-bromohexane into hexane.

A) Zn, HCl B) CuI C) H2O D) H3O+ 3-What is the conjugate base of ethanol (CH3CH2OH)? A) CH3CH2O B) CH3CH2 C) CH3CH2OH2+ D) CH3CH3 4. According to the Lewis definition, a base is a(n): A) Proton donor. B) Electron pair donor. C) Hydroxide ion donor. D) Hydrogen ion donor. 5. Which ion does not possess the electron configuration of a noble gas? A) Na+ B) H-

C) Br+ D) I-

6. Which of the acids below would have the strongest conjugate base?

A) CH3CH2OH pKa = 18 B)CH3CO2H pKa = 4.75

C)ClCH2CO2H pKa = 2.81 D)Cl2CHCO2H pKa = 1.29

7. Which of these is not a Lewis acid? A) AlCl3 B)H3O+ C) NH4+ D)C4H10

8. Which of the following is the best leaving group? A) OH- B)I- C) Br- D)F- 9. In which molecule is the central atom sp3 hybridized? A) CH4 B) NH3 C) H2O D) All of these 10. What point on the potential energy diagram below represents the least stable state for the hydrogen molecule?

A) I C)III B) II B)IV

IV-Give the scientific term of each of the following statements 1-It is the charge assigned to individual atoms in a Lewis structure. 2- It is an atom or group of atoms possessing an unpaired electron and highly reactive. 3- It is a measure of the tendency of an acid to donate a proton. 4- An organic-halogen compound has a halogen atom attached to SP2 hybrid carbon of a benzene ring 5- It is the pull of electron density through bonds caused by electronegativity differences in atoms 6- The difference in energy between the actual molecule and the energy of any of its resonance contributors. 7-A chemical bond in which orbital overlap gives a bond that is circularly symmetrical in cross section when viewed along the bond axis. 8-A quantum number that determines the energy of an orbital and has a value of n = 1, 2, 3. 9- It is the molecule or ion that is formed when an acid loses its proton. 10- It is one of the most useful and versatile reagents known to the organic chemist and considered as a source of carbanion.

Which of the following molecules can form hydrogen bond with other -V

?itselfmolecules of 1-(CH3)4N+ 2-CH3SH 3-CH3CH2OH 4-CH3COCH3 5-CH3CH2COOH

Give the IUPAC name for each compound:-VI

3- 2-1-

VII-Explain the following with writing equation whenever possible: 1-The dipole moment of chloromethane is greater (1.87 D) than the dipole

moment of the bond C-Cl (1.5 D). 2- Alkanes are good lubricants and preservatives for metals 3-Hydrogen Fluoride has a boiling point of (19.34C). Ethyl fluoride (CH3CH2F) has a larger molecular weight, yet its boiling point is (-37.7 C). 4- Alkyl halides are extremely important in organic synthesis.

order the following compounds according to what stated between brackets -VIII

(According to their boiling point) 2- Ethane methane ethyne (acetylene) (According to their acidity) 3-CH3NH2, CH3NH3 +, CH3NH- (According to their basicity)