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Question:1.Free radical halogenation of alkanes is not good method for preparation of pure alkyl halides . 2. Chloral hydrate is more stable than tri-iodo acetaldehyde . 3. Cyanohydrins are good intermediates for preparation of many organic compounds. 4.Alkyl Lithium and Grignard reagents are not stored in ether and should be freshly prepared . 5.Grignard reagent could not be prepared from Br-CH2CH2-OH

Answers:1. Because you can halogenate selectively only particularly stabilized positions, like allylic or benzylic; if you have pentane, for example, you will obtain a mixture of halopentanes (1-,2-,3-substituted). 2. Don't know what's Chloral hydrate... 3. Because you can obtain many 1,2-difunctionalized compounds by simple reactions: for hydrolisis you can obtain 2-hydroxy acids, for reduction you can obtain 2-hydroxy imines (which for hydrolisis give ketones or aldehydes) or 2-hydroxy amines, you can perform a Williamson synthesis to obtain ethers and so on... 4. Because they react a bit with ethers; because their concentration changes in the time and so you can't know how much reagent you have added exactly. 5. Because it would give an acid-base reaction with the alcohol functional group on the molecule; you can prepare it anyway by protecting the alcohol as benzyl ether (which is removed by catalytic hydrogenation).

Question:The Inheritance of Rh system is more complicated than the ABO blood group system. It is striking that most of the Indians are Rh positive. Could you explain it genetically or in some other way?

Answers:Founder effect genetic drift. Have a nice day.

Question:You probably didn't understand the question. For example -3 * -5 = 15 -3 - (-5) = 2 Why are they positive? A long explanation would be appreciated. Give lots of examples and explain WHY with lots of words and all that. Thanks in advance.

Answers:Here is the easiest way to think of it. Picture the number line or write it out. It's a line of numbers starting at 0, then proceeding to the right with positive numbers and to the left with negative numbers. When you do operations on the number line (operations meaning addition, multiplication, subtraction, and division), you start at the first number, then move to the left or right. Here is what I mean: Now, when you add two positive numbers, say 3 + 5, then you go to the right 5 spaces from 3. 3+5 = 8 When you subtract two numbers, say 3 - 5 , then you go to the left 5 spaces from 3. 3 - 5 = -3 So we see that a negative sign just means 'go the other way' on the number line. You always assume you go right, but if you see a negative sign, you go the other way. A plus sign means keep going the way you're already moving. So to translate, if you have 3 + 5, think: Start at 3. Go right. I see a + sign, so I don't change direction, and I go right 5. 3 + 5 = +8 If you have 3 - 5, think: Start at 3. Go right. But wait, I see a - sign, so I change direction, and I go left 5. 3 - 5 = -2 Now take a trickier example: -3 - (-5) Use the same logic I just mentioned. Start from -3, and assuming you go to the right. But then you see a negative sign: ok, that means switch directions, so I go left. But then there's a SECOND negative sign, which means switch AGAIN, so now I'm going right 5. Then I end up going right 5 spaces right from -3, which gives me +2. You'll notice this is exactly the same as if I had written -3 + 5. That's why a negative and negative equals a positive. It's the exact same for multiplication and division. Hope this helps

Question:Explain why Rh-negative person do not have a transfusion reaction on the first Rh-positive blood but does have a reaction on the second exposure.?

Answers:You've got it backwards. A person with Rh positive blood will not have a reaction to an Rh negative transfusion of the correct blood type because there is nothing to react to; it's negative. The protein is not there. A person with Rh- blood will react to Rh+ simply because the + protein is present and will cause a reaction.