Q:

Parent prepend SCSS

I am trying to place my selectors inside a parent. 
#top{
    /*! Single Product Page*/
    &.single-product .title_container{
        display: none;
    }

    .product_title_single{
        margin-bottom: 40px;
        h1{margin-bottom: 10px;}
    }
   ------------so on..
}

However compiled css combine all comments into parent selected separately.
#top {
    /*Slider customisation*/
    /* End Slider customisation*/
    /*Text horiziontal Ruler*/
    /*Quick Finder*/
    /*Brand Logos*/
    /*Product Category Grid*/
    /*infobox*/
    /*News Archive Page*/
    /*Blog Archive Page Search*/

}

Rest of the code is fine, is it possible to prevent this from happening?

A:

Unfortunately not.
Your example above is a good one for explaining why, however.
As the processor works its way through nested selectors, it treats any properties or comments directly nested within the top-level selector as being associated with that top-level selector.
Consider this example, (which is basically yours with the addition of the margin-top and padding-top properties, and another line after the example comment):
#top {
    margin-top: 0;

    /* a comment */

    &.single-product .title_container {
        display: none;
    }

    .product_title_single {
        margin-bottom: 40px;

        h1 {
            margin-bottom: 10px;
        }
    }

    padding-top: 0;
}

It compiles to this:
#top {
    margin-top: 0;
    /* a comment */
    padding-top: 0;
}

#top.single-product .title_container{
    display: none;
}

#top .product_title_single {
    margin-bottom: 40px;
}

#top .product_title_single h1 {
    margin-bottom: 10px;
}

Notice where padding-top: 0; ends up, even though it came after the nested selectors.
The SCSS processor treats properties and comments as "children" of the nearest "parent" selector, regardless of what precedes or follows them. It has no way of knowing that a comment is associated with any following nested selectors.
If you need your comments to remain associated with their nested selectors in the compiled output, you'll need to add the comments inside those child selectors:
#top {
    margin-top: 0;

    &.single-product .title_container {
        /* a comment */
        display: none;
    }
}

This also doesn't accomplish your real goal, however, which is to have a comment that refers to multiple following selectors, not just a single one.
You may want to shift to thinking about these comments as being more valuable to you as pre-compilation reminders, instead of keeping them around in the compiled output.
If you take that approach, try using "silent comments" with // instead of /* */ in your SCSS:
#top {
    margin-top: 0;

    // a comment
    &.single-product .title_container {
        display: none;
    }
}

Compiles to this (double-slash comments get removed during compilation):
#top {
    margin-top: 0;
}

#top.single-product .title_container{
    display: none;
}

