organic chemistry questions?

Question

Please help? jus answer the ones that you know, thanks.

1) What is the number of possible isomers for C4H8 ?
a) 6 b) 3 c) 5 d) 2
2) 1,1,2-trimethylcyclopentane is an isomer of which
compound? -a) nonane, b) isoheptane,
c) 2-isopropyl-pentane, d) isohexane
3) Which compound can react with chlorine gas to produce
1,2-dichlorocyclohexane? -a) hexane b) cyclohexene
c) 3-methylcyclohexane d) 2-methylhexane
4. When ethane is converted to ethylene, the carbon atoms:
a) are oxidized b) are reduced
c) act as oxidizers d) are unchanged
5. What is the bond angle between H-C-C in acetylene?
a) 180 b) 90 c) 109 d) 120
6. A benzene compound with a bromine in the 1 and 3
positions has the common name of:
a) o-dibromobenzene b) p-dibromobenzene
c) m-dibromobenzene d) dibromobenzene

Answer 1

(1) First of all, since the formula C4H8 conforms to the general formula of CnH2n, the compound is an alkene. Secondly,the term "isomers" has a general meaning, because there are different types of isomers.
It has 5 structural isomers;
a) H2C = CH - CH2 - CH3 ........... ( 1- butene)
a) H3C - CH = CH - CH3 ........... ( 2- butene)
c) H2C = C(CH3) - CH3 ............. ( 2-methyl 1- propen)
d) Cyclo butane (Since alkenes and cyloalkanes are isomers)
e) Methyl cyclo propane.

In addition to these,2-butene has 2 geometric isomers;
a) Cis-2-butene (Side CH3's are on the same side of the plane)
b) Trans-2-butene (Side CH3's are on the opposite sides of the plane)

But I think that only the structural isomers are asked.
ANSWER: C

(2) If you write the condensed structural formula ( it is impossible to draw a cylo structure here), you can see that it has 8 C atoms, or you can decide from the name;
Tri methyl has 3 C and the word "pentane" implies that 5 C atoms. Total makes = 8 C atom.
Nonane has 8 C atom, isoheptane has 8 C atom, 2-isopropyl-pentane has 8 C atom, isohexane has 7 C atom. Which one of the first three will be correct? NONE of them. Why?
Because cycloalkanes, as we stated above, conforms the general formula of CnH2n and they are isomers with alkenes. None of them is an alkane. If you didn't made a mistake in writing the names, no answer. But, if (a) is nonene, a is correct, if (b) is isoheptene b is correct and if (c) is 2-isopropyl-pentene, c is correct.

(3) 1,2-dichlorocyclohexane is the substitution product of cyclohexane.
ANSWER : b

(4) C2H6 ----------> C2H4 + H2
C2H6 : Each H atom has +1 charge, total +6, therefore 2 C atom must have -6 charge. Each has -3 charge.
C2H4 : Each H atom has +1 charge, total +4, therefore 2 C atom must have -4 charge. Each has -2 charge.
Since there is an increase its oxidation number, C atoms are oxidized.
ANSWER : a

(5) The acetylene molecule has a symmetrical linear structure. Therefore the cond angle is 180 degrees.
ANSWER : a

(a) In benzene molecule, the posion of the groups attached to the ring are denoted as;
1 - 2 ; ortho
1 - 3 ; meta
1 - 4 ; para
ANSWER : c

Answer 2

5 is 180 degrees

Answer 3

1) cyclobutane, methylcyclopropane, 1-butene, cis-2-butene, trans-2-butene, isobutylene

The rest I agree with.

Answer 4

This type of structure is known as "sperm".

Answer 5

1) d

2) c

3) b

4) a

5) a

6) c